A Virtual Tribute to Quark Confinement and the Hadron Spectrum 2021
With the Corona pandemic far from over and the prospect for a return to a perceived normal only at the end of 2021, the organizers of the 14th Quark Confinement and Hadron Spectrum conference have decided to postpone the in-person conference in Stavanger, Norway to August 1st - 6th, 2022 (see the ConfXIV webpage) .
At the same time the community is weathering the storm and those of us who are privileged enough can uphold their research activities. To keep the momentum of the community alive and to further exchange among practitioners in the field amidst limited options for travel, we thus invite you to join our virtual event from August 2nd-6th 2021. In the spirit of the QCHS conference series it will feature plenary talks, roundtable discussion and parallel contributed talks. Its schedule will consist of a program of reduced length of 4 hours each day, staggered from day to day, in order to accommodate a global audience.
Latest information
We will start each day with a social gathering in the digital venue before the start of the scientific program.
Start Mon & Fri 21:00h (JPN) - 14:00h (EU) - 8:00h (US East)
Start Wed 20:30h (JPN) - 13:30h (EU) - 7:30h (US East)
Start Tue & Thu. 13:00h (JPN) - 06:00h (EU) - 0:00h (US East)
Due to the Covid pandemic the event takes place at a digital venue, based on the gather.town platform. All registered participants have been sent an email containing access information to the venue.
Through the digital platform you can discuss and network with your colleagues before, after and in between the talks. At the same time the digital venue allows you to connect to the plenary talks, parallel talks and round-table discussions, which take place on zoom (see below for room list).
When entering any of the rooms of the venue, please "press the x key" on your keyboard to join the corresponding zoom session (a zoom link will be shown, click the link to join).
- Plenary sessions can be accessed via the main auditorium
- Parallels of track A can be accessed via the main auditorium
- Parallels of track B-H + focus subsection can be accessed via the correspondingly labelled rooms.
- (Exception:) Parallel VIII of track B and track D on Friday take place in room G
- The round-table discussions can be accessed via the main auditorium
We ask participants to hold your questions until the end of each talk. In the allotted question & answer time at the end of each talk you can either use the raise hand feature of zoom or write your question into the chat. The scientific chair of each session will then read your question (chat) or call you up (raise hand). Longer discussions are most conveniently conducted after the talks in the digital venue.
Please note that we will record all zoom sessions. To avoid being visible in the video, you can decide to "join without video" when entering the zoom session.
For further information on the use of the digital venue please have a look at the following instruction video:
https://www.youtube.com/watch?v=8G591Zl0tCg
There is a dedicated help desk available during the main hours of the conference, where you can get help with usage of the digital venue. If you have any technical questions regarding the digital venue, you can contact the help desk via email during the conference also: help+quarks-2021@virtualchair.net
For those of you who have signed up for the introduction to HEP masterclass outreach program. It will take place on Tuesday August 3rd 17:30h (JPN) - 11:30h (EU) - 5:30h (US East) starting off with two introductory plenary presentations accessible from the main auditorium.
The individual demonstrations will be held in the following parallel rooms:
ATLAS Z - Room B
ALICE Strangeness - Room C
Belle II - Room D
CMS - Room E
MINERvA - Room F
ALICE RAA - Room G
Particle Therapy - Main Auditorium
We are looking forward to virtually welcome all of you next week.
With best regards
on behalf of the local organizers
Alexander & Nora
I will discuss the origin of the proton mass from the Hamiltonian and gravitational form factor formulations. After examining the mass decomposition in the stress-energy-momentum tensor, it is found that the glue part of the trace anomaly can be identified as the vacuum energy from the glue condensate and gives a CONSTANT restoring pressure which balances that from the traceless part of the Hamiltonian to confine the hadron, much like the cosmological constant Einstein introduced for a static universe. From a lattice calculation of this anomaly in the charmonium, we deduce the associated string tension which turns out to be in good agreement with that from a Cornell potential which fits the charmonium spectrum.
In the past years, the light-front holographic Schrodinger Equation, of Brodsky and de Teramond, has played a role in hadronic physics analogous to that of the ordinary Schrodinger Equation in atomic physics. Its confining potential, uniquely fixed by the underlying conformal symmetry and a holographic mapping to anti-de Sitter spacetime, contains a universal emerging mass scale that governs confinement in the transverse plane and generate the hadron masses in the absence of quark masses. In this talk, I will show that non-zero quark masses and longitudinal confinement are correctly taken into account by the t Hooft Equation. The
t Hooft Equation is both consistent with, and complementary to, the holographic Schrodinger Equation. Together, this pair of equations governs hadronic spectroscopy just like the ordinary Schrodinger Equation governs atomic spectroscopy.
Spectra with full towers of levels are expected due to the quantization of the string vibrations.
We study a spectrum of flux tubes with static quark and antiquark sources for pure gauge SU(3) lattice QCD in 3+1 dimensions up to a significant number of excitations.
To go high in the spectrum, we specialize in he most symmetric case, the Σ+𝑔, use a large set of operators, solve the generalized eigenvalue and compare different lattice QCD gauge actions and anisotropies.
It is well known that a static quark-antiquark pair has a spectrum of flux-tube excitations in a pure gauge theory. In this talk I will show numerically that, in a variety of gauge Higgs theories in the non-confining Higgs phase, there is also a spectrum of excitations of the gauge and Higgs fields surrounding a static fermion-antifermion pair. These are localized and stable excitations which can exist at large fermion-antifermion separations, and which cannot decay into the ground state plus one or more vector or Higgs bosons.
Exclusive processes are traditionally described by perturbative hard blocks and
``distribution amplitudes" (DAs), matrix elements of operators of various chiral structure
and twist. One paper (with I.Zahed) calculate instanton contribution to hard blocks, which is
found comparable to perturbative one in few-$GeV^2$ $Q^2$ region of interest. Another paper
aims at comprehensive wave functions of mesons, baryons and pentaquarks. The last ones are
also included as 5-quark component of the baryons. The calculation, using 't Hooft operator,
gives x-dependence and magnitude of the antiquark PDF. It explains long standing issue
of strong flavor asymmetry of antiquark sea. The third paper (also with I.Zahed)is semi-review on
the instanton-sphaleron
processes in QCD and electroweak theories, with emphasis on their possible experimental
observation via double diffractive events at LHC and RHIC.
The majority of QCD states are unstable resonances that couple strongly to multi-particle states, with a significant fraction of these coupling to asymptotic three-particle states. Lattice QCD, being a framework that incorporates all dynamical coupling non-perturbatively, provides a promising pathway toward studying the excited states of the theory. Although challenging, lattice QCD calculations of systems composed of three-hadrons are finally being performed. In this talk, I present a calculation by the Hadron Spectrum Collaboration, Phys.Rev.Lett. 126:012001 (2021), which is the first to go from the lattice QCD correlation functions to the desired infinite-volume scattering amplitudes. I review outstanding challenges to study the low-lying resonances of QCD that couple to three particles.
Hadronic matrix elements of the QCD energy-momentum tensor can be parametrized in terms of gravitational form factors (GFFs) which, through their dependence on momentum transfer and decomposition into quark and glue contributions, encode information about the distributions of energy, angular momentum, pressure, and shear forces within a hadron spatially and amongst its constituents. GFFs can be constrained indirectly by experiments through their relation with generalized parton distributions, but they are directly and straightforwardly accessible to lattice calculations. We present the results of a recent lattice calculation at unphysically heavy pion masses of the gluonic contributions to the GFFs (and various densities derived from them) of the rho meson and delta baryon, which are as yet unconstrained by experiment, extending previous studies of the gluon GFFs of the pion and nucleon. We discuss further progress in an ongoing program of lattice calculations to determine the GFFs of the physical proton with full control over uncertaintities, including both quark and glue contributions, providing access to the physical energy, spin, pressure, and shear force densities.
We present the first determination of the hadronic decays of the lightest exotic JPC=1-+ resonance in lattice QCD. Working with SU(3) flavor symmetry, where the up, down and strange-quark masses approximately match the physical strange-quark mass giving mπ∼700 MeV, we compute finite-volume spectra on six lattice volumes which constrain a scattering system featuring eight coupled channels. Analytically continuing the scattering amplitudes into the complex-energy plane, we find a pole singularity corresponding to a narrow resonance which shows relatively weak coupling to the open pseudoscalar–pseudoscalar, vector–pseudoscalar and vector–vector decay channels, but large couplings to at least one kinematically closed axial-vector–pseudoscalar channel. Attempting a simple extrapolation of the couplings to physical light-quark mass suggests a broad π1 resonance decaying dominantly through the b1π mode with much smaller decays into f1π, ρπ, η′π and ηπ. A large total width is potentially in agreement with the experimental π1(1564) candidate state observed in ηπ, η′π, which we suggest may be heavily suppressed decay channels.
In this talk we present our recent calculation of order $\alpha_s^3$ corrections to the semi-leptonic $b\to c$ decay.
The calculation has been performed in an expansion around the heavy-daughter limit $m_c \sim m_b$, but also shows decent convergence for $m_c=0$. For the semi-leptonic $b\to c$ decay we find large perturbative corrections in the on-shell scheme which can be significantly reduced by changing to the kinetic scheme for the heavy quark masses. These results will be important input for the inclusive determination of $|V_{cb}|$ and the Fermi coupling constant $G_F$ in the future.
The mixing parameter $\Delta \Gamma_{12}^s$ is an important flavor observable that governs the lifetime difference $\Delta \Gamma_s$ of the neutral $B_s$ mesons. The state-of-the-art Standard Model prediction for $\Delta \Gamma_s$ is compatible with the HFLAV world average, yet the theoretical uncertainties due to uncalculated perturbative corrections are still large. In this talk I will report on our progress in reducing these uncertainties by calculating NNLO QCD corrections to the $B_s - \bar{B}_s$ mixing process. To this end we perform a fully analytic evaluation of the current-current correlators $P_{1,2}\otimes P_{1,2}$ at 3-loops, as well as the current-penguin $P_{1,2}\otimes P_{3,4,5,6}$ and current-chromomagnetic $P_{1,2}\otimes P_{8}$ correlators at 2-loops in the Chetyrkin-Misiak-M\"unz (CMM) basis. Some interesting aspects of this calculation to be addressed in my talk involve higher-order matching between two effective field theories ($\mathcal{H}_{\textrm{eff}}^{\Delta B = 1}$ and $\mathcal{H}_{\textrm{eff}}^{\Delta B = 2}$), dedicated treatment of evanescent operators in the presence of dimensionally regulated IR divergences, asymptotic expansion of the amplitudes in $m_c/m_b$ up to $\mathcal{O}(m_c^2)$ and the analytic evaluation of the resulting 3-loop on-shell integrals with one mass scale.
The Born-Oppenheimer approximation provides a description of heavy-quark mesons firmly based on lattice QCD, but its validity is limited to the lightest states lying far below the first open-flavour meson-meson threshold. This limitation can be overcome in the diabatic framework, a formalism first introduced in molecular physics, where the dynamics is encoded in a potential matrix whose elements can be derived from unquenched lattice QCD studies of string breaking. The nondiagonal elements of the potential matrix provide interaction between heavy quark-antiquark and meson-meson pairs, from which the mixing of quarkonium states with molecular components and the OZI-allowed strong decay widths are directly calculated. This allows for a QCD-based unified description of conventional quarkonium and unconventional mesons containing quark-antiquark and meson-meson components, what has proved to be successful for charmoniumlike [1, 2] and bottomoniumlike [3] resonances.
[1] R. Bruschini and P. González, Diabatic description of charmoniumlike mesons, Phys. Rev. D 102, 074002 (2020).
[2] R. Bruschini and P. González, Diabatic description of charmoniumlike mesons II: mass corrections and strong decay widths, Phys. Rev. D 103, 074009 (2021).
[3] R. Bruschini and P. González, Diabatic description of bottomoniumlike mesons, arXiv:2105.04401 [hep-ph] (2021).
We establish the existence of a far-from-equilibrium attractor in weakly-coupled gauge theory undergoing one-dimensional Bjorken expansion. We demonstrate that the resulting far-from-equilibrium evolution is insensitive to certain features of the initial condition, including both the initial momentum-space anisotropy and initial occupancy. We find that this insensitivity extends beyond the energy-momentum tensor to the detailed form of the one-particle distribution function. Based on our results, we assess different procedures for reconstructing the full one-particle distribution function from the energy-momentum tensor along the attractor and discuss implications for the freeze-out procedure used in the phenomenological analysis of ultra-relativistic nuclear collisions.
Motivated by the quark-gluon plasma, we develop a simulation method to obtain the spectral function of (Wilson) fermions non-perturbatively in a non-Abelian gauge theory with large gluon occupation numbers. We apply our method to a non-Abelian plasma close to its non-thermal fixed point, i.e., in a far-from-equilibrium self-similar regime, and find mostly very good agreement with perturbative hard loop (HTL) calculations. For the first time, we extract the full momentum dependence of the damping rate of fermionic collective excitations and compare our results to recent non-perturbative extractions of gluonic spectral functions in two and three spatial dimensions.
The evolution of a heavy ion collision passes close to the O(4) critical point of QCD, where fluctuations of the order parameter are expected to be enhanced. Using the appropriate stochastic hydrodynamic equations in mean field close to the
near the pseudo-critical point, we compute how these enhanced fluctuations modify the transport coefficients of QCD and make a phenomenological estimate for how chiral fluctuations could effect the momentum spectrum of soft pions. Finally, we estimate the expected critical enhancement of soft pion yields, which provides a plausible explanation for the excess seen in experiment relative to ordinary hydrodynamic computations.
Based on: arXiv:2005.02885 and 2101.10847
Search for neutrinoless double beta decay is one of the primary probes to understand the neutrino nature. Its discovery implies lepton-number violation, confirming the Majorana neutrino mass which is realized by introducing sterile neutrinos. The theoretical approach requires somewhat complicated processes connecting fundamental interactions to those at hadronic and nuclear levels. In this talk, I will discuss the systematic analyses of the neutrinoless double beta decay based on effective field theory including light sterile neutrinos.
$CP$-violating interactions at quark level generate $CP$-violating nuclear forces which could be revealed by looking at the presence of a permanent nuclear electric dipole moments. Within the framework of chiral effective field theory and thanks to the modern $ab-initio$ techniques, it is possible to perform realistic calculation for the electric dipole moment of the light nuclei. In this work we present the calculation of the electric dipole moments of ${}^2$H, ${}^3$He and ${}^3$H discussing the systematic errors introduced by the truncation of the chiral expansion. The $CP$-violating nucleon-nucleon and three-nucleon potential up to next-to-next-to leading order (N2LO) derivation will be also discussed. Moreover, we introduce some recent renormalization argument which indicates that a promotion of the short-distance operator to leading-order is needed to have a consistent picture of the $CP$-violating nuclear forces.
We describe examples of renormalizable field theories where the breaking of chiral symmetry at the UV cutoff leaves behind at low energy dynamically generated elementary particle masses in a way alternative to the Higgs mechanism. In this scenario 1) the scale of the elementary particle masses is set by the RGI scale of the theory 2) masses are kept ``small'' owing to an enhanced chiral symmetry enjoyed by the massless theory, thus solving the 't Hooft naturalness problem, 3) in order to match the experimental value of the top mass, a super-strongly interacting sector, gauge-invariantly coupled to standard matter, needs to exist with an RGI scale, $\Lambda_T\gg\Lambda_{QCD}$, of the order of a few TeV's, 4) the peculiar dependence of the non-perturbatively generated masses upon the gauge couplings is such that it may offer a hint to solve the mass hierarchy problem, 5) $\Lambda_T$ sets the order of magnitude of the electro-weak scale, 6) the 125 GeV resonance recently identified at LHC is interpreted as a $W^+W^-/ZZ$ composite state bound by exchanges of super-strongly interacting particles to which the electro-weak bosons are coupled, 7) at (momenta)$^2 \ll \Lambda_T^2$ the couplings of the composite Higgs boson with quark, leptons and electro-weak bosons coincide with those of the Standard Model up to O($\alpha_W$) corrections, 8) with a reasonable choice of particle content, a theory extending the Standard Model with the inclusion of the new super-strong sector exhibits gauge coupling unification at a scale $\sim 10^{18}$~GeV making the proton life time comfortably larger then the present limit of $1.7 \times 10^{34}$ years.
We analyze the deuteron charge and quadrupole form factors using the latest NN potentials and charge-density operators derived within chiral effective field theory. We derive relations between 1N,2N charge densities and nucleon form factors and employ several recent empirical parametrizations for proton and neutron form factors. We fit low-energy constants appearing in the fifth-order 2N charge-density operators to the world data on the shape of deuteron form factors and predict the deuteron structure radius and its quadrupole moment. Using predicted structure radius and precise data on the deuteron-proton charge-radii-difference we extract the charge radius of the neutron. A careful analysis of various sources of the uncertainties of all predictions is performed.
LA-UR-21-25112 - Neutron stars contain the largest reservoirs of degenerate fermions, reaching the highest densities we can observe in the cosmos, and probe matter under conditions that cannot be recreated in terrestrial experiments. Throughout the Universe, a large number of high-energy, cataclysmic astrophysical collisions of neutron stars are continuously occurring. These collisions provide an excellent testbed to probe the properties of matter at densities exceeding the density inside atomic nuclei, are an important site for the production of elements heavier than iron, and allow for an independent measurement of the expansion rate of our Universe.
To understand these remarkable events, reliable nuclear-physics input is essential. In this talk, I will explain how to use quantum many-body calculations employing interactions from chiral effective field theory to provide a consistent and systematic approach to neutron-star matter with controlled theoretical uncertainties.
I will present nuclear-physics predictions for the equation of state of neutron stars, and discuss how multi-messenger observations of binary neutron-star mergers can be used to further elucidate the properties of matter under extreme conditions.
The nuclear symmetry energy and its slope $L$ are fundamental quantities describing the properties of dense matter around nuclear saturation.
New measurements of the neutron-skin thickness of $^{208}\rm Pb$ have sparked recent interest in constraints on the slope of the symmetry energy, $L$, some of which can also be inferred from astrophysical systems, such as neutron star mergers.
In this talk, I will present the first systematic study of the impact of varying $L$ on the post-merger evolution of a GW170817-like neutron star merger event. More specifically, I will discuss how different values of $L$ affect the post-merger dynamics, what imprints $L$ might leave in the post-merger gravitational wave signal and how the ejection of mass during the merger is affected by it.
't Hooft anomalies provide a unique handle to study the nonperturbative dynamics of strongly-coupled theories. Although this type of anomalies was known since the 80's, recently it has been realized that one can generalize them by turning on 't Hooft twists in the color, flavor, and baryon number directions. Such generalized anomalies put severe constraints on the possible realizations of the global symmetries of a given theory in the infrared. In this talk, I will explain how one can construct such 't Hooft twists and give examples of the constrains the generalized anomalies can impose on strongly coupled gauge theories.
The connection between QCD and string theory is expected through the gauge/gravity correspondence. Particularly, it predicts that the baryons are discribed by D-branes. (This relation is analogous to the Skyrmion model where the baryons are obtained as solitons, since D-branes are also solitons in string theory.) In this talk, I will review how the D-branes behave as baryons, and discuss our attempt to obtain the nuclear states such as Deuteron and Helium from the branes.
The lattice three-gluon vertex in the Landau gauge is
revisited using a large physical volume ∼(8fm)^4 and a large statistical
ensemble. The improved calculation explores the symmetries of the
hypercubic lattice to reduce the statistical uncertainties and to
address the evaluation of the lattice artefacts. In particular we focus
on the low energy behaviour of the vertex and look at evidences for (or
not for) a change of sign and its relation with ghost dominance.
The large collaborations in high-energy physics analyze a large amount of data on a daily basis. Different practices have been consolidated and improved through the past decade. A brief overview of the most common statistical techniques used in searches for new physics and precision measurements is presented.
An overview of common statistical methods and machine learning approaches deployed at the LHCb experiment will be discussed. Particular focus will be given to recent developments using novel techniques relevant to heavy flavour physics.
We study two important properties of 2+1D QCD, namely confinement and Pseudoscalar glueball spectrum, using holographic approach. The confined state of the bounded quark-antiquark pair occurs in the self-coupling dominated nonperturbative regime, where the free gluons form the bound states, known as glueballs. The gauge theory corresponding to low energy decoupled geometry of isotropic non-supersymmetric D2 brane, which is again similar to the 2+1D YM theory, has been taken into account but in this case the coupling constant is found to vary with the energy scale. At BPS limit, this theory reduces to Supersymmetric YM theory. We have considered NG action of a test string and calculate the potential of such confined state located on the boundary. The QCD flux tube tension for large quark-antiquark separation is observed to be a monotonically increasing function of running coupling. The mass spectrum of Pseudoscalar glueball is evaluated numerically from the fluctuations of the axion in the gravity theory using WKB approximation. This produces the mass to be related to the string tension and the levels of the first three energy states. The various results that we obtained quite match with those previously studied through the lattice approach.
Quarkonia are well described by the Schrödinger equation, with a linear confining potential that agrees with lattice QCD. For QED atoms the classical $-α/r$ potential is determined by Gauss’ law. Taking the similarity with QED at face value the confinement scale of QCD should be given by a boundary condition on Gauss’ law.
Temporal gauge $(A^0=0)$ is well suited for bound states defined at equal time of the constituents. It preserves rotational invariance, allowing eigenstates of $J^2$ and $J^z$ (in the rest frame). Canonical quantization is straightforward since $\vec A$ (unlike $A^0$) has a conjugate field. In temporal gauge Gauss’ law is implemented as a constraint, not as an operator equation. It determines the value of $A_L$ for each physical state, and thus also the classical potential.
In QCD the classical color octet gluon field vanishes for color singlet states (whereas there is a dipole electric field for $e^+e^-$ states in QED). However, each color component $A$ of a $q_A\bar{q}_A$ state does have a longitudinal gluon field. There is a homogeneous solution of Gauss’ constraint in QCD which gives a spatially constant field energy density, thus preserving translational and rotational invariance for (globally) color singlet states. This leads to an instantaneous confining potential for each color compoent of the state. The potential is linear for $q\bar q$, and confining also for $qqq$, $q\bar qg$ and $gg$ states. The confinement scale is given by the magnitude of the universal field energy density.
The confining potential is of $O(α_s^0)$ and determines the strong binding of hadrons. The remaining contributions (gluon exchange, Fock states with transverse gluons and $q\bar q$ sea quarks) may be included perturbatively.
This approach to gauge theory bound states is described in arXiv 2101.06721.
We study numerically the chromoelectric-chromomagnetic asymmetry of the dimension two $A^2$ gluon condensate as well as the infrared behavior of the gluon propagators at $T\simeq T_c$ in the Landau-gauge $SU(3)$ lattice gauge theory.
We find that a very significant correlation of the real part of the Polyakov loop with the asymmetry as well as with the longitudinal propagator makes it possible to determine the critical behavior of these quantities. We obtain the screening masses in different Polyakov-loop sectors and discuss the dependence of chromoelectric and chromomagnetic interactions of static color charges and currents on the choice of the Polyakov-loop sector in the deconfinement phase.
When non-Abelian gauge fields in $SU(3)$ QCD have a line-singularity leading to non-commutability with respect to successive partial-derivative operations, the non-Abelian Bianchi identity is violated. The violation as an operator is shown to be equivalent to violation of the Abelian-like Bianchi identities. Then there appear eight Abelian-like conserved magnetic monopoles of the Dirac type in $SU(3)$ QCD. Using lattice Monte-Carlo simulations, perfect Abelian and monopole dominances are shown to exist without introducing additional smoothing techniques like partial gauge fixings when we define lattice Abelian-like monopoles following the DeGrand-Toussaint method adopted in the study of the Dirac monopole in lattice compact QED. The Abelian dual Meissner effect around a pair of static quark and antiquark is caused by the solenoidal Abelian monopole current. Preliminary results suggest that the vacuum type of the $SU(3)$ confinement phase is of Type-1.
We study the free energies of individual quarks in a finite volume with suitable boundary conditions to account for their $Z_3$-valued electric flux. In order to demonstrate how 't Hooft's electric fluxes can be used to account for Gauss' law, we first use a $Z_3$-Potts model as an effective Polyakov-loop theory for the heavy-dense limit of QCD at strong coupling, with interfaces to realize 't Hooft's twisted boundary conditions in temporal planes. The corresponding electric-flux ensembles, as discrete Fourier transforms of the temporally twisted ones, together with the static quark determinant of heavy-dense QCD are then equivalent to a modified flux-tube model. We use this equivalence to demonstrate how electric fluxes can be employed to prepare ensembles with quark numbers $N_q \not= 0 \mod 3$ in a finite volume which is impossible with periodic boundary conditions because of the Roberge-Weiss symmetry that the effective theory shares with QCD. Moreover, using dualisation techniques for the fermion determinant, we show how this construction can be generalised to full QCD with dynamical Wilson fermions. A more rigorous formulation based on the transfer-matrix approach reveals further subtleties and leaves us with a puzzle.
I will discuss recent lattice calculations of Gegenbauer moments of twist-two light cone distribution amplitudes (LCDAs) of the RQCD collaboration. There has been a lot of progress, in particular regarding taking the continuum limit and the matching to the modified minumal subtraction scheme. LCDAs play an important role in the physics of exclusive processes.
We show that using renormalization-group summation to generate the QCD radiative corrections
to the $\pi-\gamma$ transition form factor, calculated within lightcone sum rules, leads the
strong coupling free of Landau singularities while preserving the QCD form-factor asymptotics.
This enables a reliable applicability of the LCSR method to momenta well below 1~GeV$^2$.
This way, one can use the new preliminary BESIII data with unprecedented accuracy below
1.5~GeV$^2$ to fine tune the prefactor of the twist-six contribution.
Using a combined fit to all available data below 3.1~GeV$^2$, we are able to determine all
nonperturbative scale parameters and a few Gegenbauer coefficients entering the calculation
of the form factor.
Employing these ingredients, we determine a pion distribution amplitude with conformal
coefficients $(b_2,b_4)$ that agree at the $1\sigma$ level with the data for
$Q^2 < 3.1$~GeV$^2$ and fulfill at the same time the lattice constraints on $b_2$
at N$^3$LO together with the constraints from QCD sum rules with nonlocal condensates.
We suggest to probe the pion light-cone distribution amplitude, transforming the
dispersion relation for the pion electromagnetic form factor into
an equation between the spacelike form factor
$F_\pi(Q^2)$ and the integrated modulus of the timelike form factor.
For $F_\pi(Q^2)$, the QCD light-cone sum rule in terms of the
pion light-cone distribution amplitudes is used. From this equation,
employing the measured pion timelike form factor, it is possible to fit and/or constrain the Gegenbauer moments of the pion twist-2 distribution amplitude. As an independent test of our approach, we compare the spacelike pion form factor obtained in two different
ways: from the dispersion relation and from the light-cone sum rule with the measurement by the Jefferson Lab $F_\pi$ collaboration.
We study exclusive quarkonium production in the dipole picture at next-to-leading order (NLO) accuracy, using the non-relativistic expansion for the quarkonium wavefunction. This process offers one of the best ways to obtain information about gluon distributions at small x, in ultraperipheral heavy ion collisions and in deep inelastic scattering. The quarkonium light cone wave functions needed in the dipole picture have typically been available only at tree level, either in phenomenological models or in the nonrelativistic limit. In this paper, we discuss the compatibility of the dipole approach and the non-relativistic expansion and compute NLO relativistic corrections to the quarkonium light-cone wave function in light-cone gauge. Using these corrections we recover results for the NLO decay width of quarkonium to e+e− and we check that the non-relativistic expansion is consistent with ERBL evolution and with B-JIMWLK evolution of the target. The results presented here will allow computing the exclusive quarkonium production rate at NLO once the one loop photon wave function with massive quarks, currently under investigation, is known. This talk is based on Phys.Rev.D 101 (2020) 3, 034030.
We give the hyperasymptotic expansion of the energy of a static quark-antiquark pair with a precision that includes the effects of the subleading renormalon. The terminants associated to the first and second renormalon are incorporated in the analysis when necessary. In particular, we determine the normalization of the leading renormalon of the force and, consequently, of the subleading renormalon of the static potential. We obtain $Z_3^F(n_{f}= 3) = 2Z_3^V(n_{f} = 3) = 0.37(17)$. The precision we reach in strict perturbation theory is next-to-next-to-next-to-leading logarithmic resummed order both for the static potential and for the force. We find that the resummation of large logarithms and the inclusion of the leading terminants associated to the renormalons are compulsory to get accurate determinations of ${\Lambda}_{\overline{\mathrm{MS}}}$ when fitting to short-distance lattice data of the static energy. We obtain ${\Lambda}_{\overline{\mathrm{MS}}}^{\left({n}_f=3\right)}= 338(12)$ MeV and $\alpha(M_{z}) = 0.1181(9)$. We have also found strong consistency checks that the ultrasoft correction to the static energy can be computed at weak coupling in the energy range we have studied.
We apply the recently proposed nonrelativistic EFT framework for double heavy hadrons to the double heavy baryon case. The EFT is build from NRQCD by incorporating the adiabatic expansion between the light quark and the heavy quark pair. At leading order the EFT reduces to the Born-Oppenheimer approximation. The Born-Oppenheimer potentials are obtained from available lattice QCD data. We go beyond the leading order by incorporating the heavy quark spin and angular momentum operators. The corresponding potentials are obtained from their Wilson loop matching expressions by computing these in the short and long distances and interpolating the results for the intermediate region. In the short distance this is done using the multipole expansion. For the long distance we have developed an Effective String Theory with a light fermion constrained to the be in the flux tube string. Several free parameters are obtained by comparing with the spin splittings of double charm baryon lattice data and then used to predict double bottom baryon as well as excited double charm states.
Using non-relativistic QCD techniques on finite temperature lattice configurations, we will present results pertaining to the fate of the Bottom and anti-Bottom quarkonium states of Υ(1S), Υ(2S) and Υ(3S) in Quark-Gluon-Plasma (QGP). We will present results on how the mass and spectral width of these states change with temperature. We will also show new results on how the finite temperature potential between a quark and anti-quark corroborate the results obtained for the bottomonium states.
We study the transitions between the different color states of a static
quark-antiquark pair, singlet and octet, in a thermal medium. This
is done non-perturbatively exploiting the infinite mass limit of QCD. This study is interesting because it can be used
for future developments within the framework of Effective Field Theories
(EFTs) and because it can be combined with other techniques, like lattice
QCD or AdS/CFT, to gain non-perturbative information about the evolution
of quarkonium in a medium. We also study the obtained expressions
in the large $N_{c}$ limit. This allows us to learn lessons that are
useful to simplify phenomenological models of quarkonium in a plasma.
Talk based on arXiv:2010.10424
We present a comparison among various methods used to extract the spectral functions of S- and P-wave meson states from non-zero temperature NRQCD correlation functions using the FASTSUM anisotropic lattice: the maximum likelihood, Backus Gilbert, and machine learning approaches. We review the common features that can be extracted by all methods and compare the results for masses and widths.
What is the nature of so-called Dark Matter, and does it interact with regular matter except through gravity? For example, direct detection experiments aim to answer this question. Propagating measurements (or constraints) to the fundamental theory requires bridging several scales—from target nucleus to individual nucleons to the level of quarks & gluons and beyond. However, the sheer number of parameters in model-independent descriptions of DM and uncertainties associated with bridging the scales make it difficult to fully quantify uncertainties from theory to experiment. This talk exemplifies challenges associated with propagating uncertainties, focusing on the description of DM scattering off light-nuclei using chiral perturbation theory in a Bayesian context.
I will review recent developments in rare and radiative kaon decays from the theory side, with emphasis on those modes that are actively analyzed by the experimental collaborations.
In this talk we present a relativistic and model-independent method to analytically derive electromagnetic finite-size effects beyond the point-like approximation. Structure-dependence appears in terms of physical form-factors and derivatives thereof. The values of these physical quantities can be taken either from experimental measurements or auxiliary lattice calculations. We first apply our method to the meson mass, and then to leptonic decays of pions and kaons. The knowledge of the latter allows for improved numerical control in extractions of the relevant CKM-matrix elements from lattice QCD+QED.
The low-energy QCD, the theory describing the strong interaction, is still missing fundamental experimental results in order to achieve a breakthrough in its understanding. Among these experimental results, the low-energy kaon-nucleon/nuclei interaction studies are playing a key-role, with important consequences going from particle and nuclear physics to astrophysics.
Combining the excellent quality kaon beam delivered by the DANE collider in Frascati (Italy) with new experimental techniques, as fast and very precise X ray detectors, like the Silicon Drift Detectors, and with the high acceptance charged and neutral particles KLOE detector, we have performed unprecedented measurements in the low-energy strangeness sector in the framework of SIDDHARTA and AMADEUS Collaborations.
The kaonic atoms, as kaonic hydrogen and kaonic deuterium, provide the isospin dependent kaon-nucleon scattering lengths from the measurement of X rays emitted in the de-excitation process to the fundamental 1s level of the initially excited formed atom. The most precise kaonic hydrogen measurement was performed by the SIDDHARTA collaboration, which realized, as well, the first exploratory measurement for kaonic deuterium ever. Presently, a major upgrade of the setup, SIDDHARTA-2 has been realized and installed on DAFNE to perform a precise measurement of kaonic deuterium and of other exotic atoms in the coming year(s). The status of the experiment will be presented, together with future plans to extend the studies of kaonic atoms by using advanced detector systems.
The kaon–nuclei interactions are being measured by the AMADEUS collaboration for kaon momenta up to 100 MeV/c by using the KLOE detector implemented in the central region with a dedicated setup. Preliminary results for the interaction of negatively charged kaons with various type of nuclei will be shown, and future plans discussed.
The experiments at the DANE collider represents an opportunity which is unique in the world to, finally, unlock the secrets of the QCD in the strangeness sector and understand the role of strangeness in the Universe, from nuclei to the stars.
Binary Neutron Star (BNS) mergers provide a rich laboratory for the study of matter at extreme densities and temperatures. In this talk we present the results of state-of-the-art BNS simulations using modern 3-parameter (density, temperature, electron fraction) equations of state (EoSs), with particular focus on behaviour due to temperature and composition dependant effects.
First, we go over the ingredients for a BNS simulation, and how our simulations differ from the norm. We then discuss the conditions experienced by matter in such a merger event, and the implications this has for the generation of EoSs. Finally, we cover some of the physics we are attempting to study with these simulations, in particular bulk viscosity, and the difficulties in including such phenomena in simulations, such as the "true" definition of beta-equilibrium, and the need for reactions and neutrinos.
During the late stages of a neutron star binary inspiral finite-size effects come into play, with the tidal deformability of the supranuclear density matter leaving an imprint on the gravitational-wave signal. As demonstrated in the case of GW170817—the first direct detection of gravitational waves from a neutron star binary—this can lead to strong constraints on the neutron star equation of state. As detectors become more sensitive, effects which may have a smaller influence on the neutron star tidal deformability need to be taken into consideration. Dynamical effects, such as oscillation mode resonances triggered by the orbital motion, have been shown to contribute to the tidal deformability, especially close to the neutron star coalesence, where current detectors are most sensitive. We calculate the contribution of the various stellar oscillation modes to the tidal deformability and demonstrate the (anticipated) dominance of the fundamental mode. We show what the impact of the matter composition is on the tidal deformability, as well as the changes induced by more realistic additions to the problem, e.g. the presence of an elastic crust. Finally, based on this formulation, we develop a simple phenomenological model describing the effective tidal deformability of neutron stars and show that it provides a surprisingly accurate representation of the dynamical tide close to merger.
The "periodic table" of strongly coupled gauge theories remains only sketchily understood. Holography has developed to the point where bottom up constructions can describe the spectrum of individual gauge theories (based on assumptions of their running) including quarks in different representations and higher dimension operators. I highlight the method with a "perfected" version of the AdS dual of QCD and results for composite higgs models with two representations of quarks. The method highlights questions about the degree to which energy scales can be split in generic gauge theories including whether confinement and chiral symmetry breaking are linked.
Sp(4) gauge theory with two fundamental and three antisymmetric fermion flavours is a template for beyond the standard model strong interactions that can give rise to a composite Higgs boson through the breaking of the global fundamental flavour symmetry and at the same time to a partial composite top quark state that explains why the observed mass of the latter particle is at the electroweak scale. Partial top compositeness results from the mixing of the standard model top quark with a chimera baryon, i.e. a baryonic state formed with two quarks in the fundamental and one quark in the antisymmetric representation. A necessary ingredient for partial top compositeness is the generation of a large anomalous dimension for the chimera baryon. Lattice gauge theory can be used as a framework to study non-perturbatively these phenomena, in order to verify their viability beyond semi-quantitative arguments. After a brief review of the relevant analytic considerations, in this talk, I will discuss our recent numerical calculations for the target Sp(4) model, presenting results for the meson spectrum and for the chimera baryon.
In this talk I will present the results of the first numerical investigation of a gauge theory with adjoint and fundamental fermion fields. It corresponds to the heavy scalar limit of supersymmetric QCD and has further applications in composite Higgs models and semiclassical investigations of confinement. I will discuss the interplay of the different fermion representations and relations to the numerical investigations of supersymmetric gauge theories.
We present a new tensor network algorithm for calculating the partition function of interacting quantum field theories in 2 dimensions. It is based on the Tensor Renormalization Group (TRG) protocol, adapted to operate entirely at the level of fields. This strategy was applied in Ref.[1] to the much simpler case of a free boson, obtaining an excellent performance. Here we include an arbitrary self-interaction and treat it in the context of perturbation theory. A real space analogue of the Wilsonian effective action and its expansion in Feynman graphs is proposed. Using a λφ4 theory for benchmark, we evaluate the order λ correction to the free energy. The results show a fast convergence with the bond dimension, implying that our algorithm captures well the effect of interaction on entanglement.
Understanding the nature of confinement, as well as its relation with the spontaneous breaking of chiral symmetry, remains one of the long-standing questions in high-energy physics. The difficulty of these task stems from the limitations of current analytical and numerical techniques to address nonperturbative phenomena in non-Abelian gauge theories. The situation becomes particularly problematic when trying to analize the phase diagram of QCD at large Baryon densities, where a confinement-deconfinement transition between the hadronic and the quark-gluon plasma phases takes place. Recent progress with atomic quantum simulators indicates an alternative direction to overcome these limitations. In this talk, I will present two different approaches to address the physics of confinement using near-term quantum devices. In the first one, I will consider one of the simplest gauge theories in the presence of dynamical matter, and I will show how, using ideas drawn from topology, deconfinemened states can be prepared using less experimental resources [1]. In the second one, I will show how particle physics phenomenology emerges in even simpler models that do not possess gauge invariance [2], and are thus simpler to implement with atomic systems such as ultracold atoms in optical lattices. This would allow to study, for instance, confinement-deconfinement transitions and chiral symmetry restoration under controllable experimental conditions.
[1] Daniel González-Cuadra et al., Phys. Rev. X 10, 041007 (2020)
[2] Daniel González-Cuadra et al., PRX Quantum 1, 020321 (2020)
We introduce a Metropolis-Hastings Markov chain for Boltzmann distributions of classical spin systems. It relies on approximate tensor network contractions to propose correlated collective updates at each step of the evolution. We present benchmarks for a wide variety of instances of the two-dimensional Ising model, including ferromagnetic, antiferromagnetic, (fully) frustrated and Edwards-Anderson spin glass cases, and we show that, with modest computational effort, our Markov chain achieves sizeable acceptance rates, even in the vicinity of critical points. In each of the situations we have considered, the Markov chain compares well with other Monte Carlo schemes such as the Metropolis or Wolff algorithm: equilibration times appear to be reduced by a factor that varies between 40 and 2000, depending on the model and the observable being monitored. We also present an extension to three spatial dimensions, and demonstrate that it exhibits fast equilibration for finite ferro and antiferromagnetic instances. Additionally, and although it is originally designed for a square lattice of finite degrees of freedom with open boundary conditions, the proposed scheme can be used as such, or with slight modifications, to study triangular lattices, systems with continuous degrees of freedom, matrix models, a confined gas of hard spheres, or to deal with arbitrary boundary conditions. Joint work with Miguel Frías-Pérez, Michael Mariën, David Pérez García, and Mari Carmen Bañuls (arXiv:2104.13264).
The quantized vortices in superfluid confined phase may transform the large orbital momentum generated in heavy-ion collisions to the spin of baryons in the vortex core. The effect emerges only at some threshold angular velocity providing the qualitative explanation for the recent low energy data. The formation of vortex rings is considered as a mechanism of relation between local and global baryon polarization. Similarity and difference with vortices in liquid helium and interplay between condensed matter and high energy physics are discussed.
We proposed to utilize chiral anomaly [Ref. 1] for the designs of qubits potentially capable of operating at THz frequency and at room temperature. The proposed chiral qubit [Ref. 2] is a microscopic-scale ring made of a chiral semimetal, with the |0⟩ and |1⟩ states corresponding to the symmetric and antisymmetric superpositions of chiral currents circulating along the ring clockwise and counter-clockwise. In this talk, we report on the concept of our proposed chiral qubits and our investigations into several topological control principles driven by quantum coherence and understanding the time dependence of topological phase transition [Refs. 3-5]. These investigations included an experimental demonstration of a unique phonon-assisted topological switching in chiral semimetals [Ref. 3], and a discovery of a giant dissipationless topological photocurrent that carries the imprints of chiral fermions under zero magnetic field [Ref. 4]. The experimental results are compared with the dynamic phonon driving topological phases given theoretically by employing first-principles and effective Hamiltonian methods [Ref. 5].
*In collaboration with Prof. Dmitri Kharzeev of Stony Brook University
References:
[1] Q. Li et al “Chiral magnetic effect in ZrTe5” Nature Physics 12 (6), 550-554 (2016)
[2] D. Kharzeev and Q. Li “Quantum computing using chiral qubits” US Patent #10,657,456 (2020); “The Chiral Qubit: quantum computing with chiral anomaly” arXiv:1903.07133
[3] C Vaswani, et al “Light-driven Raman coherence as a nonthermal route to ultrafast topology switching in a Dirac semimetal” Physical Review X 10 (2), 021013 (2020)
[4] L. Luo et al “A light-induced phononic symmetry switch and giant dissipationless topological photocurrent in ZrTe5” Nature Materials 20 (3), 329-334 (2021)
[5] N. Aryal et al “Topological Phase Transition and Phonon-Space Dirac Topology Surfaces in ZrTe5” Physical Review Letters 126 (1), 016401(2021)
In quantum electrodynamics with charged chiral fermions, a background
electric field is the source of the chiral anomaly that can manifest
itself through the creation of a chirally imbalanced state of
fermions. This chiral state is realized through the production of
entangled pairs of right-moving fermions and left-moving antifermions
(or viceversa, depending on the orientation of the electric field).
In this talk, I will show that, at least without backreaction, the
thermodynamical Gibbs entropy associated with these pairs is equal to
the entropy of entanglement between the right-moving particles and
left-moving antiparticles. I will also derive an asymptotic expansion
for the entanglement entropy in terms of the cumulants of the
multiplicity distribution of produced particles ("full counting
statistics"), and explain how to re-sum this asymptotic expansion. I
will conclude by presenting a worked out example and study the time
dependence of the entanglement entropy in a specific time-dependent
pulsed background electric field, the so-called "Sauter pulse",
illustrate how our re-summation method works in this specific case and
find that short pulses (such as the ones created by high energy
collisions) result in an approximately thermal distribution for the
produced particles.
I discuss the relation between coupling a TQFT to Yang-Mills theory, resurgence and Lefschetz thimble decomposition. To classify the non-perturbative effects in original SU(N) theory, one must use PSU(N) bundle and lift configurations (critical points at infinity) for which there is no obstruction back to SU(N). These provide a refinement of instanton sums: integer topological charge, but crucially fractional action configurations contribute.
We analyse the properties of thermal monopoles in the high temperature phase of QCD with N_f = 2+1 flavours and physical quark masses. In particular, we determine the temperature where monopoles show condensation properties similar to those already studied in pure gauge Yang-Mills theories and related to the onset of confinement, comparing it with the temperature where chiral symmetry restoration takes place.
The mathematical method of Padé approximants is put forward to reconstruct the Borel transformed series of the correlator triggering either the tau or the Higgs decay and extract higher-order corrections in a model-independent way. The use of the D-log Padé approximants provides valuable information to its analytic structure and yields, together with the standard Padé approximants, reliable model-independent predictions of the higher-order coefficients. Such reconstruction strongly favours the use of fixed-order perturbation theory (FOPT) for the renormalization-scale setting
An enhanced phenomenological model that includes isospin-symmetry breaking is presented in this letter. The model is then used in a number of statistical fits to the most recent experimental data for the radiative transitions $V\!P\gamma$ ($V=\rho$, $K^*$, $\omega$, $\phi$ and $P=\pi$, $K$, $\eta$, $\eta^{\prime}$) and estimations for the mixing angles amongst the three pseudoscalar states with vanishing third-component of isospin are obtained. The quality of the performed fits is good, e.g. $\chi^2_{\textrm{min}}/\textrm{d.o.f} = 1.9$. The current experimental uncertainties allow for isospin-symmetry violations with a confidence level of approximately $2.5\sigma$.
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos(𝜙−𝜙𝑠) modulations provide evidence for a sizable worm-gear (II) distribution, g1T. Most of the other modulations are found to be consistent with zero with the notable exception of large sin𝜙𝑠 modulations for charged pions and positive kaons.
Recently a method of measuring static force from the lattice using an insertion of chromoelectric field to an Wilson loop has been proposed to tackle the ambiguities of taking derivative of the static potential. We present the current status of testing the viability of this approach and also expand the calculation for the first time to use gradient flow, which solves the problems with the renormalization of chromoelectric field on the lattice.
The imaginary part of the effective heavy-quark potential can be related to the total in-medium decay width of of heavy quark-antiquark bound states. We extract the static limit of this quantity using classical-statistical simulations of the real-time Yang-Mills dynamics by measuring the temporal decay of Wilson loops. By performing the simulations on finer and larger lattices we are able to show that the nonperturbative results follow the same form as the perturbative ones. For large quark-antiquark separations, we quantify the magnitude of the non-perturbative long-range corrections to the imaginary part of the heavy-quark potential. We present our results for a wide range of temperatures, lattice spacings, and lattice volumes. We also extract an estimate of the heavy-quark momentum diffusion transport coefficient from the short-distance behavior of the classical potential.
Heavy quark transport coefficients calculated from first-principles QCD are a crucial input for transport models. Utilizing the heavy quark limit, we will discuss the results of a novel approach to nonperturbatively estimate the heavy quark diffusion coefficient in a hot gluonic medium from gradient-flowed color-electric correlators on the lattice. Unlike others, this approach can be extended to a medium with dynamical fermions. The correlation functions are computed on fine isotropic lattices at $1.5\,T_\text{c}$ and are extrapolated to yield continuum data at zero flow time that is fully renormalized. Through theoretically well-established model fits we estimate the corresponding spectral function and in turn the diffusion coefficient, which is consistent with previous studies.
In this talk I will review the recent developments on the phenomenology and experimental searches for collectivity in small collision systems. For the phenomenology part I will focus on the hybrid approach based on the Color Glass Condensate (CGC) and Hydrodynamics (hydro) simulation [1]. For the experimental part my focus will be on the RHIC small system scan program [2]. I will discuss how the RHIC results indicate a dominant role of hydrodynamic final state effects on the observability of collectivity in small collision systems. However, the sub-dominant role of CGC driven correlations with an effect increasing with decreasing multiplicity is expected based on hybrid CGC+hydro calculations. I’ll briefly touch on an outstanding puzzle related to the measurements of triangular anisotropy coefficients from RHIC small system scan program.
Where do we go from here ? Several promising directions have been identified. STAR with its extended pseudorapidity acceptance has just collected data on Oxygen-Oxygen collisions at RHIC. This exploratory program promises a better understanding of the role of geometry that drives collectivity in small systems. Recently, hints of collectivity has been observed in photo-nuclear processes by studying ultra-peripheral Pb+Pb collisions [3]. Interestingly, similar processes can be studied in photo-production limits of DIS e+p/A collisions at the future Electron Ion Collider.
[1] Schenke et al, Phys.Lett.B 803 (2020) 135322
[2] Aidala C et al. (PHENIX) Nature Phys. 15 214–220
[3] Aad G et al. (ATLAS), 2101.10771 [nucl-ex]
Hadron production measurement in small collision systems (such as p+Al, p+Au, d+Au, $^3$He+Au) may allow to explore the minimal conditions for the quark-gluon plasma formation. Such research has become particularly crucial with the observation of the light hadrons collective behavior in small collision systems. Among the large variety of light hadrons, φ-meson is of particular interest since its production is sensitive to the presence of the quark-gluon plasma formation signatures. To interpret the nuclear modification effects and to study the process of the possible quark-gluon plasma formation from different perspectives the comparisons with theoretical model predictions are needed. Current report presents the comparison of the obtained experimental results on φ-meson production in small collision systems (p+Al, p+Au, d+Au, $^3$He+Au) at $\sqrt{s_{_{NN}}} = 200$ GeV to default and string melting versions of the AMPT model and PYTHIA 8.3/Angatyr model predictions. The results suggest that system volume and lifetime in p+Au, d+Au, and $^3$He+Au collisions are sufficient for the small quark-gluon plasma droplet formation, whereas p+Al collisions are well described in the absence of hot and dense matter effects.
The quantitative understanding of hadron structure holds the key to the interpretation of current and future experiments in particle, hadron and nuclear physics, which provide crucial information for the search for New Physics. In this talk I review the status of lattice QCD calculations of structural properties of the nucleon, focussing on the determination of electromagnetic and axial form factors, calculations of the axial, scalar and tensor charges, as well as the determination of sigma-terms. A central issue for precision calculations of these quantities is control over excited state contributions that may cause a systematic bias in results.
The axial, scalar, and tensor charges of the nucleon are important observables needed to interpret the results of many experiments and probe new physics. In this talk, I will present our recent lattice QCD calculations of the nucleon charges and discuss systematic uncertainties associated with the excited state contamination.
In this work, we focus on identifying which conditions generate massive stars and how these affect the radii and tidal deformability of intermediate and massive stars. We build equations of state either from realistic models with exotic degrees of freedom or in a model-independent approach, using a functional form of the speed of sound and discuss cross-overs, first-order phase transitions, and different kinds of twin-star solutions. We focus on the implications of GW190814 as a neutron-star constraint, but also discuss GW170817, J0030+0451, J0740+6620, and the binary companion to V723 Mon.
In this talk I will revisit modified and direct Urca
processes in nuclear matter under conditions that we expect in neutron
star mergers. Nuclear Urca processes have shown to be a potential
significant source of bulk viscosity under merger conditions. I will
explain how a correct relativistic treatment can alter the rates and
the true beta equilibrium significantly, and present a new way to deal
with in-medium effects for modified Urca.
We present the results concerning analytic (3+1)-dimensional inhomogeneous and topologically nontrivial pion systems hosting topologically stable baryons. This phase, relevant for the core of compact stars featuring a pion condensed core, is discussed within two-flavor leading order chiral perturbation theory.
We review dilaton chiral perturbation theory (dChPT), the low-energy theory for the light sector of near-conformal, confining theories. dChPT accounts for the pions and the light scalar,and provides a systematic expansion in both the fermion mass and the distance to the conformal window. Unlike ChPT, dChPT predicts a large-mass regime in which the theory exhibits hyperscaling,while the expansion nevertheless remains systematic. We discuss applications to lattice data, presenting successes as well as directions for future work.
I review attempts at constructing models of partial compositeness from strongly coupled gauge theories.
A few minimality assumptions allow one to isolate a small number of prototypical models.
After presenting the main idea, I discuss a recent proposal to detect a light ALP, predicted in all these models, at the LHCb detector.
The maturity era of lattice quantum field theory simulations brings in ample potential both to explore theories beyond QCD, and to investigate the qualitative workings of QCD by opening up the parameter space. We will focus on studying hadronic interactions and weak decays as a function of the number of colours, with four dynamical quark flavours. This shines light on classic problems such as the \Delta I=1/2 rule, or the dynamics of spontaneous chiral symmetry breaking.
In lattice QCD simulations, a large number of observables are calculated on each Monte Carlo sample of gauge fields, and their statistical fluctuations are correlated with each other as they share the same background gauge field. By exploiting the correlation, a machine learning regression model can be trained to predict the values of the computationally expensive observables from the values of the computationally cheap observables for each Monte Carlo sample of the gauge field. I will present the machine learning algorithm and its applications to the prediction of lattice QCD observables and discuss the bias correction and error quantification procedure of the machine learning predictions on statistical data.
Critical slowing down and topological freezing are key obstacles to progress in lattice QCD calculations of hadronic properties causing the cost of ensemble generation to severely diverge in the continuum limit. Recently, a class of machine learning techniques known as flow-based models has been successfully applied to produce exact sampling schemes that can circumvent critical slowing down and/or topological freezing in purely bosonic proof-of-principle applications. I will briefly summarize these flow-based MCMC methods and discuss progress towards including the contributions of fermionic degrees of freedom in this method, required for example to include dynamical quark contributions to flow-based sampling for lattice QCD.
We study the machine learning techniques applied to the lattice gauge theory's critical behavior, particularly to the confinement/deconfinement phase transition in the SU(2) and SU(3) gauge theories. We find that the neural network, trained on lattice configurations of gauge fields at an unphysical value of the lattice parameters as an input, builds up a gauge-invariant function, and finds correlations with the target observable that is valid in the physical region of the parameter space. In particular, we show that the algorithm may be trained to build up the Polyakov loop which serves an an order parameter of the deconfining phase transition. The machine learning techniques can thus be used as a numerical analog of the analytical continuation from easily accessible but physically uninteresting regions of the coupling space to the interesting but potentially not accessible regions.
The Casimir energy and profile of the QCD flux-tube are discussed within the framework of Lüscher-Weisz (LW) string action with two boundary terms. We perform our numerical simulations on the 4-dim pure SU(3) Yang-Mills lattice gauge theory at finite temperature. The static quark-antiquark ($Q\bar{Q}$) potential is calculated using link-integrated Polyakov loop correlators. In general, we detect signatures of the two boundary terms of the string action. Near the QCD Plateau, the L\"uscher-Weisz string is yielding a static potential which is in a good agreement with the lattice data for source separations $R \ge 0.3$ fm. At higher temperature, near to the deconfinement point $T/T_{c}=0.9$, the fits to the potential data improve compared to the pure Nambu-Goto string. Good match with the numerical data are retrieved at color source separation $R > 0.6$ fm; however, deviations from the string tension $\sigma_{0} a^{2}$ parameter persist. The mean-square width of the energy profile at $T/T_{c}=0.9$ is well fitted to the width of the L\"uscher-Weisz string at leading or next-to-leading order over distance scales $R \ge 0.5$ fm provided considering either two or one boundary term corrections for each order, respectively.
In this work, we analyzed a recent proposal to detect SU(N) continuum Yang-Mills sectors labeled by center vortices, inspired by Laplacian-type center gauges in the lattice. Initially, after the introduction of appropriate external sources, we obtained a rich set of sector-dependent Ward identities, which can be used to control the form of the divergences. Next, we were able to show the all-order multiplicative renormalizability of the center-vortex free sector. These are important steps towards the establishment of a first principles, well-defined, and calculable Yang-Mills ensemble.
We study the quark-gluon vertex in the limit of vanishing gluon momentum using lattice QCD with 2 flavors of O(a) improved Wilson fermions, for several lattice spacings and quark masses. We fi?nd that all three form factors in this kinematics have a signi?cant infrared strength, and
that both the leading form factor ?1, multiplying the tree-level vertex structure, and the scalar,
chiral symmetry breaking form factor ?3 are signi?cantly enhanced in the infrared compared to the
quenched (Nf = 0) case. These enhancements are orders of magnitude larger than predicted by
one-loop perturbation theory. We ?nd only a weak dependence on the lattice spacing and quark
mass.
We discuss the effects of rotation on confining properties of gauge theories focusing on compact electrodynamics in two spatial dimensions as an analytically tractable model. We show that the rotation leads to a deconfining transition at finite temperature starting from a certain distance from the rotation axis. We argue that the uniformly rotating confining system possesses, in addition to the usual confinement and deconfinement phases, a mixed inhomogeneous phase that hosts spatially separated confinement and deconfinement regions. Implications of our results for the phase diagram of QCD are presented.
Decomposition of SU(2) gauge field into monopole and monopoleless components is studied in SU(2) gluodynamics and in QC_2D with nonzero quark chemical potential after fixing MA gauge. For both components we calculate respective static potential and compare their sum with the nonabelian static potential. We demonstrate good agreement in the confinement phase and discuss the implications of our results.
We investigate the single transverse-spin asymmetry with a $sin(2\phi-\phi_S)$ modulation in the pion-induced Drell-Yan process within the theoretical framework of the transverse momentum dependent (TMD) factorization. The asymmetry is contributed by the convolution of the Boer-Mulders function and the transversity. We adopt the model results for the distributions of the pion meson and the available parametrization for the distributions of the proton to numerically estimate the $sin(2\phi-\phi_S)$ asymmetry in $\pi^-p$ Drell-Yan at the kinematics of COMPASS at CERN. To implement the TMD evolution formalism of the distribution functions, we apply two different parametrizations on the nonperturbative Sudakov form factors associated with the distribution functions of the proton and the pion. It is found that our prediction on the single transverse-spin dependent asymmetry $sin(2\phi-\phi_S)$ as functions of $x_p$, $x_\pi$, $x_F$ and $q_\perp$ is
qualitatively consistent with the recent COMPASS measurement in both sign and magnitude.
The Belle II experiment at the SuperKEKB energy-asymmetric $e^+ e^-$ collider is an upgrade of the B factory facility at KEK in Tsukuba, Japan. The experiment began operation in 2019 and aims to record a factor of 50 times more data than its predecessor. Belle II is uniquely capable of studying the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now number in the dozens, and represent the emergence of a new category within quantum chromodynamics. We present recent results in new Belle II data, and the future prospects to explore both exotic and conventional quarkonium physics.
The nature of the three narrow hidden-charm pentaquark $P_c$ states, i.e., $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, is under intense discussion since their discovery from the updated analysis of the process $\Lambda_b^0\to J/\psi p K^-$ by LHCb. We employ an coupled-channel approach to study the $P_c$ states observed by LHCb Collaborations in the molecuar picture, in which the $P_c$ states are treated as $\Sigma_c\bar{D}^{(*)}$ molecules, by including the $\Lambda_c\bar{D}^{(*)}$ and $\eta_c p$ in addition to the $J/\psi p$ as explicit inelastic channels as required by unitarity and heavy quark spin symmetry (HQSS), respectively. Since inelastic parameters are very badly constrained by the current data, different calculation schemes are considered. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with $S$-wave-to-$D$-wave mixing contact terms. As a result, in line with our previous analysis, we demonstrate that the experimental data for the $J/\psi p$ invariant mass distribution are consistent with the interpretation of the $P_c(4312)$ and $P_c(4440)/P_c(4457)$ as $\Sigma_c\bar{D}$ and $\Sigma_c \bar{D}^{*}$ hadronic molecules, respectively, and that the data show clear evidence for a new narrow state, $P_c(4380)$, identified as a $\Sigma_c^* \bar D$ molecule, which should exist as a consequence of HQSS. However, now two solutions are found in all schemes which describe the data equally well, and thus no unambiguous conclusion about the quantum numbers of the $P_c(4440)$ and $P_c(4457)$ from data in the $J/\psi p$ channel alone is possible. It is argued though that one of these solutions, in which the quantum numbers of the $P_c(4440)$ and $P_c(4457)$ are $J^P=3/2^-$ and $1/2^-$, respectively, is theoretically preferred. Moreover, we demonstrate that the line shapes related to the $P_c(4440)$ and the $P_c(4457)$ in the $\Sigma_c^{(*)}\bar{D}$ and $\eta_c p$ mass distributions from $\Lambda_b^0\to \Sigma_c^{(*)}\bar{D} K^-$ and $\Lambda_b^0\to \eta_cp K^-$ will allow one to pin down the quantum numbers in the hadronic molecular picture, once the data are available. We also investigate possible pentaquark signals in the $\Lambda_c \bar{D}^{(*)}$ final states.
In order to understand the nature of the XYZ particles, theoretical predictions of the various decay modes of the XYZ measured by experiments are essential. In this work, we focus on the decay of heavy quarkonium hybrids. We study semi-inclusive decays of heavy quarkonium hybrids into traditional quarkonium in the EFT framework. We found that our numerical results of the decay rates are different from previous studies. We also develop a calculation framework in which the theoretical uncertainty can be systematically improved.
Precise knowledge of the thermodynamic properties of zero-temperature, high-density quark matter (QM) can constrain the neutron-star-matter equation of state (EOS), even at much lower densities. However, current bounds on this QM EOS suffer from rather large uncertainties stemming from renormalization-scale dependence. In this talk, I will lay out how to improve the dense QM EOS beyond N2LO, and how to disentangle contributions to the pressure at N3LO. At this higher order, interactions involving the dynamically screened, long-wavelength (soft) gluon modes in loop corrections can contribute. I will present the fully soft contribution to the pressure stemming from self-interactions between these long-wavelength, screened gluons. This soft sector is well-behaved at high density, contrary to the case encountered at high temperatures, and this new contribution slightly decreases the renormalization-scale dependence of the EOS at high density.
We investigate the thermal QCD phase transition and its scaling properties on the lattice. The simulations are performed with N_f=2+1+1 Wilson twisted mass fermions at pion masses from physical up to heavy quark regime. We introduce a new chiral order parameter, which is free from linear mass contributions and turns out to be useful for the study of scaling behaviour. Our results are compatible with O(4) universal scaling for the physical pion mass and the temperature range [120:300] MeV. Violations to scaling at larger masses and other possible scenarios, including mean field behaviour and Z(2) universality class are also discussed. We provide an estimation for the critical temperature in the chiral limit T_0.
In addition to the well known-sign problem, methods currently used to study finite baryon density lattice QCD suffer from additional uncontrolled systematics, coming e.g. from the analytic continuation problem one faces with the Taylor or imaginary chemical potential methods. We formulate and test a new method - sign reweighting - that works directly at finite chemical potential and is free from any such uncontrolled systematics. In particular it is free of the overlap problem, which bottlenecked more traditional reweighting methods so far. With this approach the only problem is the sign problem itself. As a first test, we apply the method to calculate the position of the critical endpoint on a coarse lattice: unimproved staggered fermions at $N_\tau=4$; as a second application, we also study the phase diagram with 2stout improved staggered fermions at $N_\tau=6$. This second one is already a reasonably fine lattice - relevant for phenomenology.
Recently, we established an $N\bar N$ potential within chiral
effective field theory [1] which is fitted to up-to-date $N\bar N$
phase shifts and inelasticities provided by a recently published
phase-shift analysis of available $p \bar p$ scattering data [2].
The quality of the description of those phase shifts but also
of $p \bar p$ observables will be discussed.
As an application of this interaction neutron-antineutron oscillations
in the deuteron are considered [3].
In particular, results for the deuteron lifetime will be presented,
evaluated in terms of the free-space $n-\bar n$ oscillation time,
utilizing that $N\bar N$ potential together with an $NN$ interaction
likewise derived within chiral effective field theory.
[1] Ling-Yun Dai, J. Haidenbauer, U.-G. Meißner, JHEP 07 (2017) 078.
[2] D. Zhou, R.G.E. Timmermans, Phys.Rev.C 86 (2012) 044003.
[3] J. Haidenbauer, U.-G. Meißner, Chin.Phys.C 44 (2020) 033101.
Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy $\sqrt{s}=319$ GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of $136$ pb$^{-1}$. Charged particle multiplicities are measured as a function of photon virtuality $Q^2$, inelasticity $y$ and pseudorapidity $\eta$ in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of $Q^2$ and the Bjorken variable $x_{\rm Bj}$ are converted to the hadron entropy $S_{\rm hadron}$, and predictions from a quantum entanglement model are tested.
Eur.Phys.J.C 81 (2021), 212
Effective Field Theories (EFTs) organized as derivative expansions are controllable as long as the energy of the interacting particles remains small, as they do not respect exact elastic unitarity. This limits their predictive power towards new physics at a higher scale if small separations from the Standard Model are found at the LHC or elsewhere.
This is exemplified by ChPT: though nominally the EFT could be extended to a sizeable value below 4 pi F (about 1.2 GeV) the p-wave expansion stops converging little above threshold because of the presence of the strong rho(770) resonance.
Unitarized chiral perturbation theory extends the EFT reach to regimes where partial waves saturate unitarity, but its systematic uncertainty is unknown.
We address this shortcoming for the Inverse Amplitude Method (IAM), and carefully following its dispersive derivation, we quantify the uncertainty introduced at each step. We compare its hadron ChPT and its electroweak sector Higgs EFT applications.
We find that the relative theoretical uncertainty of the IAM at the mass of the first resonance encountered in a partial-wave is of the same order in the counting as the starting uncertainty of the EFT at near-threshold energies, so that its unitarized extension should a priori be expected to be reasonably successful.
A prerequisite is to provide a check for zeroes of the partial-wave amplitude before applying the method and, if any appear near the resonance region, we show how to adequately modify the IAM to take them into account.
Thus, if the LHC experiments were to measure a separation from the SM of WLWL or hh scattering encoded in HEFT coefficients, the IAM could be used to extrapolate to higher energies with a measure of theoretical control.
Within General Relativity there is a maximum latent heat for a first order phase transition that a neutron star can support, the Seidov limit. If neutron-star matter exceeds it, the transition to the presumed exotic phase will not be complete before the star undergoes gravitational collapse.
However, this limit should generally be different in theories of modified gravity, that are to be tested in neutron star interiors (the place where the stress-energy tensor is largest). It is then interesting to ascertain what is the strongest possible phase transition, as quantified by its latent heat, that hadron physics can still allow on its own.
For this we apply the nEoS sets developed by us in collaboration with Mark Alford and Andreas Windisch https://doi.org/10.1088/1361-6471/ab2567 and that rely on extant ChPT and pQCD calculations (in the respective low- and high-density limits) and first principles alone, without reference to any astrophysical observables, making them free of assumption about the theory of gravity at the star.
We obtain a bound on the maximum latent heat as function of the density (at zero temperature) at which the phase transition triggers, independently of GR. It is currently less tight than the Seidov limit and can serve as a benchmark for future progress on the equation of state from hadron physics alone.
Holographic techniques are particularly fit to analyzing matter at extreme conditions where QCD matter is strongly coupled. Combining predictions of the holographic model with state-of-the-art effective field theory models of nuclear matter, I construct a family of feasible "hybrid" equations of state which cover both the quark matter and nuclear matter phases. The model predicts, among other things, that the NICER's radius measurement is fully consistent with the absence of quark matter inside massive neutron stars.
In this talk, we study a bottom-up holographic model where nuclear matter is realized as a dilute gas of deformed instantons in six dimensions. In the probe approximation, we obtain a stiff equation of state for the nuclear matter, where the speed of sound is relatively large. Based on the above observation, Tolman-Oppenheimer-Volkov (TOV) equation is solved numerically and then we find the mass-radius (M-R) relation, which is similar to that of quark matter. This is a result specific to our holographic model.
I will discuss the muon anomalies that have been persisting in data in the recent years, namely the muon g-2 and the lepton flavour non-universality in B decays, in the context of strongly coupled theories. I will show that these anomalies are natural in composite theories of the Higgs sector of the Standard Model. In particular, the characteristic scale of 2 TeV emerging from the muon g-2 points straightly to technicolor-like theories.
With non-perturbative lattice calculations we investigate the finite-temperature confinement transition of a composite dark matter model. We focus on the regime in which this early-universe transition is first order and would generate a stochastic background of gravitational waves. Future searches for stochastic gravitational waves will provide a new way to discover or constrain composite dark matter, in addition to direct-detection and collider experiments. As a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.
In this talk I will describe dark sectors made of non-abelian gauge theories with fermions neutral under the Standard Model. This leads to accidentally stable Dark Matter candidates that can be populated minimally through gravitational interactions. In the pure glue scenario DM is the lightest glueball while adding light fermions the lightest pion and baryon are the DM candidates.
Despite the absence of SM interactions these scenarios are constrained by structure formation, Neff and limits on DM self-interactions.
The unsupervised search for overdense regions in high-dimensional feature spaces, where locally high population densities may be associated with anomalous contaminations to an otherwise more uniform population, is of relevance to applications ranging from fundamental research to industrial use cases. Motivated by the specific needs of searches for new phenomena in particle collisions, we propose a novel approach that targets signals of interest populating compact regions of the feature space. The method consists in a systematic scan of subspaces of a standardized copula of the feature space, where the minimum p-value of a hypothesis test of local uniformity is sought by gradient descent. We characterize the performance of the proposed algorithm and show its effectiveness in several experimental situations.
Matrix inversion problems are often encountered in experimental physics, and in particular in high-energy
particle physics, under the name of unfolding. The true spectrum of a physical quantity is deformed by
the presence of a detector, resulting in an observed spectrum. If we discretize both the true and observed
spectra into histograms, we can model the detector response via a matrix. Inferring a true spectrum
starting from an observed spectrum requires therefore inverting the response matrix. Many methods exist
in literature for this task, all starting from the observed spectrum and using a simulated true spectrum as
a guide to obtain a meaningful solution in cases where the response matrix is not easily invertible.
In this Manuscript, I take a different approach to the unfolding problem. Rather than inverting the
response matrix and transforming the observed distribution into the most likely parent distribution in
generator space, I sample many distributions in generator space, fold them through the original response
matrix, and pick the generator-level distribution which yields the folded distribution closest to the data
distribution. Regularization schemes can be introduced to treat the case where non-diagonal response
matrices result in high-frequency oscillations of the solution in true space, and the introduced bias is
studied.
The algorithm performs as well as traditional unfolding algorithms in cases where the inverse problem
is well-defined in terms of the discretization of the true and smeared space, and outperforms them in
cases where the inverse problem is ill-defined—when the number of truth-space bins is larger than that of
smeared-space bins. These advantages stem from the fact that the algorithm does not technically invert
any matrix and uses only the data distribution as a guide to choose the best solution.
The algorithm is also extended, in analogy to Bayesian approaches such as Metropolis Hastings, to a full description of the posterior distribution of each bin yield.
Calculating analytic properties of Euclidean propagators is a demanding task, in particular if one considers non-perturbative approaches, such as Dyson-Schwinger equations. At the same time, once calculated in the complex domain, these correlators provide valuable insights into various properties associated with the proagating degree of freedom, and can serve as input to bound state equations. In order to compute those amplitudes in the complex domain, the integration path of the radial component of the loop momentum in the self energy has to be deformed away from the real axis in order to avoid non-analyticities such as poles and/or cuts. While in perturbative settings such deformations can be found manually, this is not feasible when it comes to iterative approaches applied to solve self-consistent integral equations. Utilizing the powerful machinery of Deep Reinforcement Learning, we demonstrate that an autonomous agent can be trained to perform such contour deformations. With our study we provide a proof of principle that such an agent could be deployed in a non-perturbative, iterative setup to compute analytic properties through suitably and automatically deformed integral contours.
We discuss vortex solutions in the non-Hermitian parity-time-symmetric relativistic model with two interacting scalar complex fields. In the London limit, the vortex singularities in different condensates experience dissipative dynamics unless they overlap. At finite quartic couplings, the vortices appear in the PT-symmetric regions with broken U(1) symmetry. We find the phase diagram of the interacting model where the PT-symmetric and PT-broken regions together with the U(1)-symmetric and U(1)-broken phases form complicated patterns.
Statistical models are a powerful tool for investigation of complex system's behaviour. Most of the models considered in the literature are defined on regular lattices with nearest neighbour interactions. The models with nonlocal interaction kernels have been less studied. In our study we investigate an example of such a model - the nonlocal $q$-color Potts model on a random $d=2$ lattice. Only same color spins at unit distance (within some margin $\delta$) interact. The goal is to find minimum energy configuration starting from some random coloring of the sites. We present the results of supercomputer simulations of this system and discuss the corresponding patterns. Conjectured relation with the problem of finding the chromatic number of the plane is discussed.
The broken inversion symmetry of underlying crystals of non-centrosymmetric superconductors gives rise to new nontrivial phenomena, such as magnetoelectric effects and helical phases. We study non-centrosymmetric superconductor using the Ginzburg-Landau effective model supplemented with a parity-odd Lifshitz term. We show that these parity-odd superconductors possess knotted solitons in a form of a self-linked magnetic field, which resemble Chandrasekhar-Kendall states in astrophysical plasma. We present explicit analytical solutions for material with the crystallographic $O$ - point group. We find that the magnetic field in these solutions is not quantized. The spatial distribution of the supercurrent is demonstrated.
String tension is one of the characteristic quantity in confining gauge theories. In SU(N) gauge theories, there is a center symmetry, or $\mathbb{Z}_N$ 1-form symmetry, which acts on the test quarks, and this is the symmetry which controls the spectral properties of confining strings in the infrared regime. This is sometimes called as an $N$-ality rule.
In this talk, I will talk about some models of confining gauge theories, where the N-ality rule is violated. That is, the center symmetry is again given by Z_N as in the case of SU(N) theory, while the confining strings of Wilson loops carry detailed information on their representations beyond N-ality. Then, I will uncover that those models enjoy the non-invertible symmetry, and they can naturally explain why the N-ality rule can be violated. I would also like to talk about speculation on possible applicability to non-Abelian gauge theories in higher dimensions.
This talk is based on the works, https://arxiv.org/abs/2101.02227 and https://arxiv.org/abs/2104.01824, in collaboration with Mendel Nguyen and Mithat Unsal.
Quark confinement mechanism is one of unsolved important problems. In the dual Meissner picture of color confinement, it is considered that the color flux tube between static quarks is caused by the condensation of color magnetic monopoles in the QCD vacuum. In this talk, we show new results of the dual Meissner effect due to the violation of non-Abelian Bianchi identity corresponding to Abelian Dirac-type monopoles in QCD. In particular, we discuss the vacuum type by evaluating the Ginzburg-Landau parameter through the measurements of Abelian electric field and Abelian squared monopole density in pure SU(3) gauge theory without gauge fixing.
When investigating confinement in the Coulomb gauge on the lattice, one encounters some difficulties in devising a suitable definition of the dispersion relations for Wilson fermions. In this talk we will discuss a solution to this problems based on a redefinition of the lattice physical momentum of the fermion.
A complete theoretical analysis of the $C$-conserving semileptonic decays $\eta^{(\prime)}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ ($l=e$ or $\mu$) is carried out within the framework of the Vector Meson Dominance (VMD) model. An existing phenomenological model is used to parametrise the VMD coupling constants and the associated numerical values are obtained from an optimisation fit to $V\to P\gamma$ and $P\to V\gamma$ radiative decays ($V=\rho^0$, $\omega$, $\phi$ and $P=\pi^0$, $\eta$, $\eta^{\prime}$). The decay widths and dilepton energy spectra for the two $\eta\to\pi^0l^+l^-$ processes obtained using this approach are compared and found to be in good agreement with other results available in the published literature. Theoretical predictions for the four $\eta^{\prime}\to\pi^0l^+l^-$ and $\eta^\prime\to\eta l^+l^-$ decay widths and dilepton energy spectra are calculated and presented for the first time in this work. Finally, the signature of CP violating operators from the SMEFT on experimental observables is investigated and quantified for the $l=\mu$ case.
We have recently completed the coupled dispersive analysis of $\pi K$ pi pi -> K anti-K data.
We show that just fitting data fails to satisfy the dispersive representation and leads to inconsistencies with threshold sum-rules as well as unreliable resonance parameterizations.
Our main result is a set of constrained fits to data that satisfy 16 dispersion relations of different kinds and allow for a reliable extraction of threshold and subtreshold parameters to be compared with Chiral Perturbation Theory and lattice QCD. In addition, we obtain a precise dispersive determination of the controversial light kappa-meson parameters, which has therefore become a "confirmed" state in the PDG, completing the light meson scalar nonet. The constrained fits to data are easy to implement and ready for further theoretical and experimental studies.
We extract the diffusion coefficient $\kappa$ and the resulting momentum broadening $\langle p^2 \rangle$ of a heavy quark embedded in a far-from-equilibrium gluon plasma using classical statistical lattice simulations. We find several features in the time dependence of the momentum broadening: a short initial rapid growth of $\langle p^2 \rangle$, followed by linear growth with time due to Langevin-type dynamics and damped oscillations around this growth at the plasmon frequency. We show that these novel oscillations are not easily explained using perturbative techniques but result from an excess of gluons at low momenta. These oscillation are therefore a gauge invariant confirmation of the infrared enhancement we had previously observed in gauge-fixed correlation functions. We argue that the kinetic theory description of such systems becomes less reliable in the presence of this IR enhancement.
We have developed a self-consistent theoretical approach to study the modification of the properties of heavy mesons in hot mesonic matter which takes into account chiral and heavy-quark spin-flavor symmetries. The heavy-light meson-meson unitarized scattering amplitudes in coupled channels incorporate thermal corrections by using the imaginary-time formalism, as well as the dressing of the heavy mesons with the self-energies [1, 2]. As a result, the open heavy-flavour ground-state spectral functions broaden and their peak is shifted towards lower energies with increasing temperatures. I will discuss the implications for the excited mesonic states generated dynamically in this heavy-light molecular model. In addition I will show meson Euclidean correlators calculated using the thermal ground-state spectral functions obtained with this methodology and their comparison with recent open-charm lattice correlators [3].
[1] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, Phys. Lett. B 806 (2020), 135464 doi:10.1016/j.physletb.2020.
[2] G. Montaña, A. Ramos, L. Tolos and J. M. Torres-Rincon, Phys.Rev.D 102 (2020) 9, 096020 doi:10.1103/PhysRevD.102.096020
[3] G. Montaña, O. Kaczmarek, L. Tolos and A. Ramos, Eur.Phys.J.A 56 (2020) 11, 294 doi:10.1140/epja/s10050-020-00300-y
We revisit previous determination of the strong coupling constant from moments
of quarkonium correlators in (2+1)-flavor QCD. We use
previously calculated moments obtained with Highly Improved Staggered
Quark (HISQ) action for five different quark masses and several lattice spacings.
We perform a careful continuum extrapolations of the moments and from the comparison
of these to the perturbative result we determine the
QCD Lambda parameter, $\Lambda_{\overline{MS}}^{n_f=3}=332 \pm 17 \pm 2(scale)$ MeV. This
corresponds to $\alpha_s^{n_f=5}(\mu=M_Z)=0.1177(12)$.
I will give a brief review on the theory of jet quenching and discuss some recent progress toward measuring quark and gluon jet modification in heavy-ion collisions.
The interaction of a jet with the medium created in heavy-ion collisions is not yet fully understood from a QCD-perspective. This is mainly due to the nonperturbative nature of this interaction which affects both, transverse jet momentum broadening and jet quenching.
We review how lattice simulations of Electrostatic QCD can be properly extrapolated to the continuum, which operators to measure and extract from the data, and how to promote these operators to full, fourdimensional QCD. Finally, we show how these results translate to phenomenological calculations.
In this talk, I will report on our numerical lattice simulations of partons traversing the boost-invariant, non-perturbative glasma as created at the early stages of collisions at RHIC and LHC [1]. Since these highly energetic partons are produced from hard scatterings during heavy ion collisions, they are already affected by the first stage of the medium's time evolution, the glasma, which is the pre-equilibrium precursor state of the quark-gluon plasma. We find that partons quickly accumulate transverse momentum up to the saturation momentum during the glasma stage. Moreover, we observe an interesting anisotropy in transverse momentum broadening of partons with larger broadening in the rapidity than in the azimuthal direction. Its origin can be related to correlations among the longitudinal color-electric and color-magnetic flux tubes in the initial state of the glasma. I will compare these observations to the semi-analytic results [2] obtained by a weak-field approximation, where we also find such an anisotropy in a parton's transverse momentum broadening.
[1] A. Ipp, D. I. Müller, D. Schuh, Phys. Lett. B 810 (2020), arXiv:2009.14206
https://doi.org/10.1016/j.physletb.2020.135810
[2] A. Ipp, D. I. Müller, D. Schuh, Phys. Rev. D 102 (2020), arXiv:2001.10001
https://doi.org/10.1103/PhysRevD.102.074001
In this talk I will provide a brief review of the different results and approaches used in estimating the contributions to the anomalous magnetic moment of the muon, with emphasis on the hadronic contributions. The presentation will follow the review released by the Muon g-2 Theory Initiative.
Model-independent short-distance constraints allow for a reduction of theoretical uncertainties associated to the analytic evaluation of Hadronic Light by Light contributions to muon g-2. In this talk we focus on the region where the three loop virtualities are large. Even when the fourth photon leg is soft, we show how a precise Operator Product Expansion can be applied in that region. The leading contribution is found to be given by the quark loop, while the evaluation of both gluonic and power corrections show how the expansion is well behaved at relatively low energies, where significant contributions to muon g-2 remain. Numerical values for them are also presented.
In recent years, significant progress in the calculation of the HLbL contribution to the anomalous magnetic moment of the muon has been achieved both with data-driven methods and in lattice QCD. In the talk I will discuss current developments aimed at controlling HLbL scattering at the level of 10%, as required for the final precision of the Fermilab E989 experiment.
We present the unified equation of state with induced surface tension (IST) that reproduces the nuclear matter properties, fulfills the proton flow constraint, provides a high-quality description of hadron multiplicities created during the nuclear-nuclear collision experiments, and is equally consistent with NS observations. Obtained tidal Love numbers are in full agreement with the constraints deduced from the observations of the binary NS mergers. Moreover, we demonstrate the IST EoS to be consistent with the universality of the I-Love-Q relations. Cooling simulations for isolated neutron star show very good agreement with astrophysical observations.
I present the results of a systematic investigation of the possible locations for the neutron star special point (SP), a unique feature of hybrid neutron stars in the mass-radius. The study is performed within the two-phase approach where the high-density (quark matter) phase is described by the constant-sound-speed (CSS) equation of state (EoS) and the nuclear matter phase around saturation density is varied from very soft (APR) to stiff (DD2 with excluded nucleon volume). In this study we demonstrate the invariance of the SP to the details of the onset of deconfinement (be it a 1st order phase transition or crossover interpolation construction). The utility of this unique feature of hybrid stars is explored by means of a derived relation between the SP mass and the maximum mass of non-rotating neutron stars, as well as possible implications in the context of GW170817 and the novel NICER measurement of PSR J0740+6620.
Taking into account experimental data, theoretical calculations and neutron star observations to constrain the equation of state several properties of neutron stars will be discussed, in particular: possible properties of hybrid stars, the influence of hyperonic degrees of freedom on the cooling of neutron stars, the presence of light clusters in the warm equation of state and the effect of the magnetic field on the crust core transition.
Working in sectors of large global charge leads to important simplifications when studying strongly coupled CFTs.
In this talk I will introduce the large-charge expansion via the simple example of the O(2) model and apply it in a number of other situations displaying a richer structure, such as asymptotically safe theories and walking dynamics.
A deformation of pure Yang-Mills theory by a phantom field similar to the
Faddeev-Popov ghost is considered. In this theory an Ersatz-supersymmetry
is identified which results in cancellation of quantum corrections up to two-
loop order. A quadruplet built from two complex fields in the adjoint – the
Faddeev-Popov ghost and the phantom Φ, all with the wrong statistics – balances four gauge fields a. At this level, the instanton measure and the β function is fully determined by quasiclassics. In a simple φ4 theory with a phantom added I identify a strictly conserved Ersatz-supercurrent. In the latter theory unitarity of amplitudes persists despite the presence of the phantom. In deformed Yang-Mills it is likely (although not proven) to persist too in all amplitudes with only gluon external legs. It remains to be seen whether this construction is just a device facilitating some loop calculations or broader applications can be found.
One of the main limitations in particle physics analyses with ML-based selection is the understanding of the implications of systematic uncertainties. The usual approach being the training using samples without systematic effects and estimating their contribution to the magnitudes measured on modified test samples. We propose here a method based on data augmentation to incorporate the systematics at the training time, which provides both an improvement in the performance and a reduction in the biases.
The statistical significance that characterizes a discrepancy
between a measurement and theoretical prediction is usually
calculated assuming that the statistical and systematic
uncertainties are known. Many types of systematic uncertainties
are, however, estimated on the basis of approximate procedures and
thus the values of the assigned errors are themselves uncertain.
Here the impact of the uncertainty {\it on the assigned uncertainty}
is investigated in the context of the muon $g-2$ anomaly. The
significance of the observed discrepancy between the Standard Model
prediction of the muon's anomalous magnetic moment and measured
values are shown to decrease substantially if the relative
uncertainty in the uncertainty assigned to the Standard Model
prediction exceeds around 30\%. The reduction in sensitivity
increases for higher significance, so that establishing a $5\sigma$
effect will require not only small uncertainties but the
uncertainties themselves must be estimated accurately to correspond
to one standard deviation.
Evaluating extremely low p-values with importance sampling techniques in discovery-oriented HEP analyses.
Many results in current particle physics studies are derived using asymptotic approximations to calculate the p-value (or the significance) of the hypothesis tested. It is difficult to ensure to which extent the requirements for these approximations are valid in cases where the number of observations is not large, for binned fits with lowly populated bins or when there are non-gaussian nuisances with a significant contribution. The common alternative of estimation with pseudo-experiments becomes unattainable if the usual “5-sigma significance” is to be claimed.
A technique is proposed to overcome this problem, which permits a precise estimation of very low p-values with a modest number of pseudo-experiments for realistic cases and taking advantage of the expected signal model.
The Muon g-2 Experiment (E989) at Fermi National Accelerator Lab- oratory (FNAL) has measured the muon anomalous precession frequency (a_μ) in its first physics run in 2018 with a precision of 0.46 parts per million. The anomalous precession frequency was measured using the in- tensity variation of positrons from the decay of polarized positive muons circulating around a storage ring. The magnetic field in the storage ring is actively and passively shimmed to be highly uniform, and it is monitored using nuclear magnetic resonance probes that are calibrated in terms of the equivalent proton spin precession frequency in a spherical water sam- ple. An ensemble of Muon Campus beamline, injection, and storage ring simulation packages were used to develop and test the systematic corrections and errors arising from beam dynamics. In June 2021, the experi- ment completed its fourth physics run. This talk will present an update on the most recent running periods and the plans for the future.
Symmetry is a key concept in physics. Some symmetries exist however only in the classical world and can not be realized in the quantum theory. When this happens we speak of a (quantum) anomaly. The most prominent examples are the triangle anomalies arising the quantum field theory of chiral fermions. In particle physics they explain the short lifetime of the neutral pion, give rise to consistency conditions on gauge theories and allow powerful insight into the low energy
dynamics. Over the last decade it has bee realized that anomalies also give rise to dissipationless transport phenomena in hot and dense relativistic matter. I will review this anomalous transport theory and then discuss how it can be applied to the electronics of Weyl semimetals.
The anomalous currents of two and three-flavor chiral nuclear matter in the presence of chiral imbalance are computed, using recently developed methods based on differential geometry techniques exploiting generalized transgression, which facilitates the evaluation of both the equilibrium partition function and the covariant currents. The constitutive relations for both the broken and unbroken phase of the theory are studied and the out-of-equilibrium nondissipative transport coefficients determined. In the broken/confined phase, the vector covariant currents exhibit nondissipative chiral electric, magnetic, and vortical effects, the latter governed by chiral imbalance.
This work is based on Ref. [1,2]. Other references are [3-4].
[1] J.L. Mañes, E. Megias, M. Valle, M.A. Vazquez-Mozo, JHEP 1912 (2019) 018. arXiv: 1910.04013[hep-th].
[2] J.L. Mañes, E. Megias, M. Valle, M.A. Vazquez-Mozo, JHEP 1811 (2018) 076. arXiv: 1806.07647[hep-th].
[3] K. Fukushima and K. Mameda, Phys. Rev. D86 (2012) 071501, arXiv: 1206.3128.
[4] T. Brauner and H. Kolesova , Nucl. Phys. B945 (2019) 114676. arXiv:1809.05310.
Suspended graphene provides an example of strongly correlated chiral fermions in 2+1D, and the logarithmic renormalization of the Fermi velocity in the infrared limit is one of the most prominent consequences of electron-electron interaction. For the first time, we could directly reproduce this effect in fully non-perturbative Quantum Monte Carlo (QMC) calculations using as large as 102x102 lattices, which gave us access to the scales approaching those of experiments on real graphene samples. We compared our QMC results with experiment and demonstrated the agreement if the finite-temperature corrections and the screening of the short-range electron-electron interactions by higher bands are taken into account. These results, now validated by experiment, are subsequently compared with multi-loop perturbative calculations made within the Lattice Perturbation Theory (LPT) and in continuum QED. We demonstrate the importance of both lattice-scale physics and diagrammatic corrections beyond Random Phase Approximation for the quantitative description of the Fermi velocity renormalization. We also discuss the finite-temperature corrections, which appear to be of the opposite sign in perturbative series and in non-perturbative QMC signaling about possible breakdown of perturbation theory in strongly-correlated QED.
The $SU(2)$ Lattice Gauge Theory in $(2+1)$ dimensions is a perfect laboratory to study the fine details of the confining interquark potential. In this talk I will first discuss a few important properties of the effective string theory and then I will compare its predictions with the results of some recent high precision montecarlo simulations of the $SU(2)$ LGT, looking for possible corrections beyond the Nambu-Goto model.
The vacuum of quantum chromodynamics has an incredibly rich structure at the confinement scale, which is intimately connected with the topology of gauge fields, and put to a stringent test by the strong CP problem. We investigate the long distance properties of the theory in the presence of a topological $\theta$ term. This is done on the lattice, using the gradient flow to isolate the long distance modes in the functional integral measure and tracing it over successive length scales. We find that the color fields produced by quarks and gluons are screened for vacuum angles $|\theta| > 0$, thus providing a natural solution of the strong CP problem.
High statistics samples from modern experiments triggered an essential work on revisiting theoretical models and tools applied to analyze the resonance phenomena of QCD.
In this talk, I will discuss two exotic-resonance candidates, $a_1(1420)$ and $\pi_1(1600)$ cleared up over the last few years using data of the COMPASS experiment.
With our recent analysis [hep-ph:2006.05342], the $a_1(1420)$ candidate is concluded to be consistent with the manifestation of the Triangle Singularity (TS) in the coupled system of 3pi and KKpi. The TS mechanism, claimed to be responsible for the appearance of the several XYZ states in the charmonium spectrum,
is usually difficult to test due to unknown couplings and production rates. In contrast, the description of the $a_1(1420)$ is nearly-model independent due to the known pair-wise interaction of the light hadrons. It makes the $a_1(1420)$ the best test ground for our understanding of the TS, the fundamental field-theory phenomenon.
The pole of the $\pi_1(1600)$ resonance was established recently by the JPAC group in the analysis of $\eta^{(\prime)}\pi$. I will present new work on relating the appearance of this exotic state to the exchange dynamics in $\eta^{(\prime)}\pi$ system showing the particle-force duality for the exotic state [hep-ph:2104.10646].
We study the hidden-charm pentaquark states $udsc\bar{c}$ with spins 1/2, 3/2, and 5/2 within the QCD sum-rule approach. We construct the currents for the particular configuration of the pentaquark states that consist of the flavor singlet three-quark cluster $uds$ of spins 1/2 and 3/2 and the two-quark cluster $\bar cc$ of spin 1, where both clusters are in a color-octet state. From the QCD sum rules, obtained by the operator product expansion up to dimension-10 condensates, we have extracted masses for the pentaquark states
$udsc\bar{c}$ and $udcu\bar c$.
New data from BESIII and LHCb indicate the existence of two hidden charm, open strangeness resonances, dubbed Zcs(3985) and Zcs(4003). Their quasi-degeneracy reproduces, in the strange quark sector, the situation observed with X(3872) and Zc(3900) in the u,d quark sector. The Zcs resonances neatly fit into two broken SU(3)f symmetry nonets with JP = 1+ and opposite charge-conjugation. The mass of the missing element of the nonets is predicted. A short overview of the field will be given.
Hadron spectroscopy is an important tool to study quark dynamics by various hadron properties such as resonance mass, spin, parity, angular momentum, etc. In addition to these, magnetic moments and various possible decay channels are of keen interest to know the intrinsic interaction. A potential model is used to determine these properties for a particular hadron, and the results are compared with experimental findings. Here, a non-relativistic hypercentral Constituent Quark Model has been employed to obtain radial and orbital excited states of light baryons from octet and decuplet families. The potential term consists of Coulomb-like term and confining term taken as linear as well as correction term has been added. So far, the results have been obtained for N, Δ, Ξ, Λ, Σ baryons and compared with available experimental results. Also, Regge trajectories have been plot for the calculated mass and assigned spin-parity to obtain the linear curve. The magnetic moment for the ground state have been evaluated using the effective mass. Some of the light strange baryons have scarce experimental known states. Thus, upcoming experimental facilities such as PANDA are expected to reveal more unknown states which shall give opportunity to corroborate the present findings.
rest at LEAR, the CERN-Munich multipoles for $\pi\pi$ elastic scattering, the $S$-wave from BNL data on $\pi\pi$ scattering into $K_SK_S$, and from GAMS data on $\pi\pi\to \pi^0\pi^0, \eta\eta$, and $\eta\eta'$. The analysis reveals the existence of ten scalar isoscalar resonances. The resonances can be grouped into two classes: resonances with a large SU(3) singlet component and those with
a large octet component. Their production of isoscalar resonances with a large octet component is suppressed in radiative $J/\psi$ decays. However, in a limited mass range centered at 1850\,MeV, these mesons are produced abundantly. Mainly-singlet scalar resonances are produced over the full mass range but with larger intensity at 1850\,MeV. The total scalar isoscalar yield in radiative decays into scalar mesons shows a clear peak which is interpreted as the scalar glueball of lowest mass.
Soft gluon factorization (SGF) is a new approach to describe heavy quarkonium production and decay. As the SGF resums a series of velocity corrections in NRQCD approach, it is expected to have a better perturbative convergence. In this talk, I will discuss the application of SGF for both exclusive quarkonium production and inclusive quarkonium production. The result shows that the SGF has a potential to explain puzzles in the quarkonium field.
I will present our work on the application of a combination of soft collinear effective theory and non-relativistic QCD to observables in quarkonium production and decay that are sensitive to soft gluon radiation, in particular measurements that are sensitive to small transverse momentum. Ultimately the aim is to use this approach to study quarkonium production in hadronic collisions at small transverse momentum. In my talk I will present the simpler scenario where a chi_c decays to light quarks followed by the fragmentation of those quarks to light hadrons. This example has all the elements of hadronic production: factorization involving transverse momentum dependent parton distribution, fragmentation functions and new quarkonium shape functions. It also has large logarithms both in invariant mass and rapidity that can be resumed.
In this talk we will present several quarkonium polarization measurements that the CMS collaboration has made, in the bottomonium and charmonium families. Emphasis will be given to the most recent measurements, including the result on the chi_c1 and chi_c2 polarizations.
NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a fixed-target experiment operating at the CERN SPS accelerator. The main goal of the strong interactions program of NA61/SHINE is to study the properties of the phase transition between confined matter and quark-gluon plasma by performing a two-dimensional scan in beam momentum and size of collided nuclei. Within this program, collisions of different systems (p+p, p+Pb, Be+Be, Ar+Sc, Xe+La, Pb+Pb) over a wide range of beam momenta (13A-150(8)A GeV/c) have been recorded.
This contribution will discuss the latest results of hadron production in p+p, Be+Be, Ar+Sc and Pb+Pb reactions measured by the NA61/SHINE. In particular, the results include charged kaons and pions spectra, anisotropic flow, higher-order moments of multiplicity and net charge distributions. The presented data will be compared with the predictions of different theoretical models as well as the results from other experiments. Finally, the motivation and plans for future NA61/SHINE measurements will be discussed.
We discuss the behaviour of a universal combination of susceptibility and correlation length in the Ising model in two and three dimensions, in presence of both magnetic and thermal perturbations, in the neighbourhood of the critical point. In three dimensions we address the problem using a parametric representation of the equation of state. In two dimensions we make use of the exact integrability of the model along the thermal and the magnetic axes. Our results can be used as a sort of "reference frame" to chart the critical region of the model.
While our results can be applied in principle to any possible realization of the Ising universality class, we address in particular, as specific examples, instances of Ising behaviour in finite temperature QCD related in various ways to the deconfinement transition. Most notably, we study the critical ending point in the finite density, finite temperature phase diagram of QCD. In this finite density framework, due to well know sign problem, Montecarlo simulations are not possible and thus a direct comparison of experimental results with QFT/Statmech predictions like the one we discuss may be important. Moreover in this example it is particularly difficult to disentangle "magnetic-like" from "thermal-like" observables and thus an explicit charting of the neighbourhood of the critical point can be particularly useful.
In relativistic nuclear collisions the production of hadrons with light (u,d,s) quarks is quantitatively described in the framework of the Statistical Hadronization Model (SHM). Since charm quarks are dominantly produced in initial hard collisions but interact strongly in the hot fireball, charmed hadrons can be incorporated into the SHM by treating charm quarks as 'impurities' with thermal distributions, with the total charm content of the fireball fixed by the measured open charm cross section. We demonstrate that this way the measured multiplicities of single charm hadrons in Pb-Pb collisions at LHC energies can be well described with the same thermal parameters as for (u,d,s) hadrons. Furthermore, transverse momentum distributions are computed in a hydrodynamic approach also incorporating resonance decays. The approach is extended to lighter collision systems down to O-O and includes doubly- and triply-charmed hadrons. We show predictions for production probabilities of such states exhibiting a characteristic and rather spectacular enhancement hierarchy.
The concept of lepton universality, where the muon and tau particles are simply heavier copies of the electron, is a key prediction in the Standard Model (SM). In models beyond the SM, lepton universality can be naturally violated with new physics particles that couple preferentially to the second and third generation leptons. Over the last few years, several hints of lepton universality violation have been seen in both b->c and b->s semileptonic beauty decays. This presentation will review these anomalies and give an outlook for the near future. Other probes of NP in highly suppressed b-hadron decays will also be discussed.
Motivated by the experimental patterns of lepton-universality breaking, we present a simple strategy based on ratios of leptonic and semileptonic B decays which decouple the CKM elements $|V_{ub}|$ and $|V_{cb}|$ from the short-distance coefficients of (pseudo)-scalar, vector and tensor operator contributions associated with $b \rightarrow u$ and $b \rightarrow c$ transitions. We illustrate our strategy with different hypothetical model-independent scenarios and propose ratios for observables related with the $b \rightarrow u$ transitions with the aim of further constrain the possible new physics contributions. Moreover our results derived when studying the $b \rightarrow c$ processes lead to predictions for yet unmeasured $B_{c}$ leptonic decays. In all the cases we asses the values of $|V_{ub}|$ and $|V_{cb}|$ as well.
In the context of warped five-dimensional models formulated to understand the physics beyond the Standard Model (SM), we will discuss the prediction of a continuum of Kaluza-Klein modes, on top of the SM zero modes, with different mass gaps for all particles: gauge bosons, fermions, graviton, radion and Higgs boson. In particular, we will study the existence of resonance effects in gauge bosons. The model can be considered as a modelization in five dimensions of gapped unparticles. We compute the Green's functions and show how they can modify some SM processes. We also discuss some applications for Dark Matter. This work is based on Refs. [1-2]. Other related references are [3-7].
[1] E. Megias, M. Quiros, "Gapped continuum Kaluza-Klein spectrum", JHEP 1908 (2019) 166. arXiv:1806.04877 [hep-ph].
[2] E. Megias, M. Quiros, "Gapped continuum Kaluza-Klein spectrum", arXiv:2146.10260 [hep-ph].
[3] L. Randall, R. Sundrum, “A Large mass hierarchy from a small extra dimension”, PRL 83 (1999) 3370-3373.
[4] C. Csaki et al., “Continuum Naturalness”, JHEP 1903 (2019) 142.
[5] C. Csaki et al., "Continuum Dark Matter", arXiv:2105.07035 [hep-ph].
[6] G. Giudice et al, “Clockwork/Linear Dilaton: Structure and Phenomenology”, JHEP 1806 (2018) 009.
[7] L. Randall and G. Servant, "Gravitational waves from warped space", JHEP 0705 (2007), 054.
I will discuss the properties of some spatially inhomogeneous phases in hadronic matter at finite densities
Chiral perturbation theory is a low-energy effective theory for QCD that gives
model-independent prediction in its region of validity. In this talk, I will present recent progress in two and three-flavor chpt at finite isospin density.
This is includes thermodynamic quantities, quark, and pion condensates, and phase diagrams, all calculated at next-to-leading order. The results are compared with
recent high-precision lattice simulations and the agreement is generally very good.
We point out a novel configurations in holographic QCD, allowing baryons to coexist with fundamental quarks. The resulting phase is a dual realization of quarkyonic matter, which is predicted to occur in QCD at a large number of colors, and possibly plays a role in real-world QCD as well. We find that holographic quarkyonic matter is chirally symmetric and that, for large baryon chemical potentials, it is energetically preferred over pure nuclear matter and over pure quark matter. Finally, we also discuss recent findings about holographic baryonic matter with isospin asymmetry, including fully dynamically its interplay with pion condensation.
In this talk I present our progress on lattice gauge equivariant convolutional neural networks (L-CNNs). These new types of neural networks are a variant of convolutional neural networks (CNNs) which exactly preserve lattice gauge symmetry. By explicitly accounting for parallel transport in convolutions and allowing for bilinear operations inside the network, we show that L-CNNs can be used to approximate any gauge covariant function on the lattice. We demonstrate that our L-CNN models vastly outperform traditional CNNs in regression tasks such as computing Wilson loops from lattice gauge field configurations. In addition, we show that our L-CNN models can be trained on data from small lattices while still performing well on larger lattices.
[1] "Lattice gauge equivariant convolutional neural networks", M. Favoni, A. Ipp, D. I. Müller, D. Schuh, https://arxiv.org/abs/2012.12901
The crucial role played by the underlying symmetries of high energy physics and lattice field theories calls for the implementation of such symmetries in the neural network architectures that are applied to the physical system under consideration. In this talk we focus on the consequences of incorporating translational equivariance among the network properties, particularly in terms of performance and generalization [1]. The benefits of equivariant networks are exemplified by studying a complex scalar field theory, on which various regression and classification tasks are examined. For a meaningful comparison, promising equivariant and non-equivariant architectures are identified by means of a systematic search. The results indicate that in most of the tasks our best equivariant architectures can perform and generalize significantly better than their non-equivariant counterparts, which applies not only to physical parameters beyond those represented in the training set, but also to different lattice sizes.
[1] ``Generalization capabilities of translationally equivariant neural networks'', S.~Bulusu, M.~Favoni, A.~Ipp, D.~I.~Müller, D.~Schuh,
https://arxiv.org/abs/2103.14686
We solve the Lindblad equation describing the Brownian motion of a Coulombic heavy quark-antiquark pair in a strongly coupled quark-gluon plasma using the highly efficient Monte Carlo wave-function method. The Lindblad equation has been derived in the framework of pNRQCD and fully accounts for the quantum and non-Abelian nature of the system. The hydrodynamics of the plasma is realistically implemented through a 3+1D dissipative hydrodynamics code. We compute the bottomonium nuclear modification factor and compare with the most recent LHC data. The computation does not rely on any free parameter, as it depends on two transport coefficients that have been evaluated independently in lattice QCD. Our final results, which include late-time feed down of excited states, agree well with the available data from LHC 5.02 TeV PbPb collisions.
Since the first positive measurement of the Λ-hyperon global spin polarization in heavy-ion collisions by STAR in 2017, the understanding of the nature of this phenomenon is one of the most intriguing challenges for the community. As relativistic fluid dynamics celebrates multiple successes in describing collective dynamics of the QCD matter in such reactions, the natural question arises whether the spin dynamics can also be modeled in such a framework. In this talk, the motivation for and recent outcomes of the experimental hunt for the macroscopic footprints of quantum spin in the relativistic heavy-ion collisions will be presented and the theoretical challenges connected with formulating its collective description will be discussed.
The spinodal instability is a prime signal for the first-order phase transition with negative speed of sound squared $cs^2$ in the Quantum-ChromoDynamics phase diagram relevant for the RHIC energy scan. In recent studies [1,2], one evolves planar unstable black branes dual to a plasma with a first order phase transition subject to the spinodal instability. Near a critical point the interface between cold and hot stable phases, given by its width and surface tension, features a wider phase separation and a smaller surface tension. Far away from a critical point the formation time of the spinodal instability is reduced. Across softer and harder phase transitions, I demonstrate that mergers of equilibrated peaks and unstable plateaux lead to the preferred final single phase separated solution.
Refs:
[1] https://arxiv.org/abs/2012.15687
[2] https://arxiv.org/abs/1905.12544
It depends: While we find within holography that the lifetime of the magnetic field for collider energies like the ones achieved at RHIC is long enough to build up the chiral magnetic current, the lifetime of the magnetic field at LHC seems to be too short. We study the real time evolution of the chiral magnetic effect out-of-equilibrium in strongly coupled holographic gauge theories. We consider the backreaction of the magnetic field onto the geometry and monitor pressure and chiral magnetic current. Our findings show that generically at small magnetic field the pressure builds up faster than the chiral magnetic current whereas at strong magnetic field the opposite is true. At large charge we also find that equilibration is delayed significantly due to long lived oscillations. We also match the parameters of our model to QCD parameters and draw lessons of possible relevance to the realization of the chiral magnetic effect in heavy ion collisions. In particular, we find an equilibration time of about ∼0.35 fm/c in presence of the chiral anomaly for plasma temperatures of order T∼300−400 MeV.
It is known since long that hydrodynamic flow in the directions of an external gravitational force and gradient of temperature are related to each other. We consider generalizations to the cases of higher orders in hydrodynamic expansion and/or to higher orders in acceleration. We demonstrate in particular that the vortical effect in presence of gravity is reproduced via the equivalence principle while usually it is ascribed to the so called gravimagnetic anomaly. A crucial point is existence of extra conservation laws in case of non-dissipative fluids. We comment also on the duality between evaluation of various matrix elements in case of equilibrium physics and motion in external gravitational force.
In this work, we shall analyze mixed ensembles formed by percolating oriented
and nonoriented center-vortices in three and four dimensions. In particular, we suggest that the inclusion of the natural interactions and possible matching rules are responsible for the emergence of topological solitons that accommodate an asymptotic Casimir scaling law and the observed flux tube profiles.
Confinement remains one the most interesting and challenging nonperturbative phenomenon in non-Abelian gauge theories. Recent semiclassical (for $SU(2)$) and lattice (for QCD) studies have suggested that confinement arises from interactions of statistical ensembles of instanton-dyons with the Polyakov loop. In this talk, I will present recent work which has extended the study of semiclassical ensemble of dyons to the $SU(3)$ Yang-Mills theory. It will be shown that such interactions do generate the expected first-order deconfinement phase transition. The properties of the ensemble, including the dyon correlations and densities, and the topological susceptibility, are studied over a range of temperatures above and below $T_c$. Additionally, the dyon ensemble is studied in the Yang-Mills theory containing an extra trace-deformation term. It will be shown that such a term causes the theory to remain confined even at high temperatures.
Results for the ground states and excited states of glueballs in Yang-Mills theory with $J^{\pm+}$, J=0,1,2,3,4, from Bethe-Salpeter equations are presented. The input comes from parameter-free Dyson-Schwinger calculations of the propagators and vertices. We compare with the corresponding lattice results and add some excited states to the known spectrum.
I summarize recent work pointing towards the existence of a universal holographic light-front wavefunction for light mesons and nucleons. This holographic wavefunction, which describes simultaneously a bound state in light-front QCD and the propagation of string modes in a dilaton-modified 5-dimensional anti de Sitter spacetime, is a specific realization of the gauge-gravity duality. The modification of the holographic wavefunction by the spin structures specific to mesons and nucleons, leads to a remarkable simultaneous description of EM transition form factors of light mesons as well as the Dirac and Pauli form factors of nucleons.
A purely data-driven fit of J/psi, psi(2S) and chi_c1,2 measurements reported by ATLAS and CMS, including the recently measured chi_c decay distributions, constrains the polarization of the directly produced J/psi mesons to a remarkably small and pT-independent value: lambda_theta = 0.04 +- 0.06. If this observation of seemingly unpolarized quarkonium production is confirmed by more precise polarization measurements, we may be be seeing a significant violation of the non-relativistic QCD (NRQCD) velocity scaling rules, which determine the magnitudes of the colour octet contributions. Can the NRQCD factorization expansion be made compatible with such an observation? Whatever the answer, high-precision polarization measurements will improve our fundamental understanding of quarkonium production.
We compute the color singlet and color octet NRQCD long-distance matrix elements for inclusive production of P-wave quarkonia in the framework of pNRQCD. In this way, the color octet NRQCD long-distance matrix element can be determined without relying on measured cross section data, which has not been possible so far. We obtain inclusive cross sections of χcJ and χbJ at the LHC, which are in good agreement with data. In principle, the formalism developed in this work can be applied to all inclusive production processes of heavy quarkonia.
Experimental measurements of multiplicity fluctuations are used to extract information about the properties of the quark-gluon plasma and transition to the hadron gas phase in heavy-ion collisions. In particular, the event-by-event fluctuations of conserved quantities within a fixed rapidity range can be related to thermodynamic properties of the medium, allowing for direct comparison to lattice QCD predictions, and used to explore the phase diagram of nuclear matter. In this talk, the latest experimental results on multiplicity and net particle fluctuations from RHIC and the LHC will be presented and placed into context with recent theoretical developments, and future prospects will also be discussed.
We will discuss thermal modifications of charmonium and bottomonium spectral properties in a hot gluonic medium from continuum extrapolated lattice results. The dissociation temperatures of quarkonia as well as charm and bottom quark diffusion coefficients are presented in the temperature region from 1.1$T_c$ to 2.25$T_c$ in the quenched approximation with valence quarks tuned to physical $J/\psi$ and $\Upsilon$ masses. The results are obtained by incorporating theoretically and perturbatively inspired models for the spectral functions compared to continuum extrapolated correlation functions measured on the lattice.
In recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma (QGP), using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here the quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the system reduced density matrix.
We investigate the real-time dynamics of a correlated heavy quark-antiquark pair inside the QGP using a quantum master equation previously derived from first QCD principles in [1]. The full equation is directly resolved in 1D to lessen computing costs and is used for the first time to gain insight on the dynamics in both a static and evolving medium following a Björken-like temperature evolution. The role of color degrees of freedom will be studied by comparing the case of a QED and QCD plasma. Several parametrizations will be explored, by modifying the initial state (color state of the pair, initial excited state...) or the complex potential used.
[1]-J. P. Blaizot and M. A. Escobedo, Quantum and classical dynamics of heavy quarks in a quark-gluon plasma, J. High Energy Phys. 06 (2018) 034.
The existence of CP violation in the decays of strange and beauty mesons is very well established experimentally. On the contrary, CP violation in the decays of charmed particles has been elusive for a long time for the experimentalists and has been observed before for the first time in 2018 by the LHCb experiment. During the LHC Run 1 and Run 2, the LHCb collaboration has collected a huge samples with charm hadron decays, on a scale never seen before. These sample enable the most sensitive searches for CP violation ever performed. In the presentation, previous results from Run 1 will be reviewed and the innovative model-independent technique of searching for CP violation in charm baryon decays will be discussed and compared to other well-known methods such as \chi^2 test. A new technique is implemented and tested on a toy model that allowed the production of generated samples for different values of CP asymmetry. The LHCb proton-proton collision data, after appropriate selection procedure are tested as well. The offline, the detector asymmetries and other reconstruction effects will be discussed in detail. The performance of the χ2 method will be also demonstrated using data.
We discuss the theoretical implications of the recent discovery of CP violation in two-body charm decays at LHCb. The 2019 breakthrough follows the first discovery of CP violation in kaon decays in 1964 and in beauty decays in 2001. We illustrate that charm physics has the potential for the discovery of physics beyond the Standard Model and will teach us also more about non-perturbative low-energy QCD.
Strong magnetic fields are relevant for both systems where QCD matter can be studied in practice - heavy ion collisions and neutron stars. The ground state of QCD at zero temperature, in sufficiently strong magnetic fields and at moderate baryon densities was recently shown to carry a crystalline condensate of neutral pions: the chiral soliton lattice. This phase of matter might be relevant for magnetars; however, in order to assess its relevance for heavy ion collisions, finite temperature has to be taken into account. In this talk, I will describe the effects of quantum fluctuations and finite temperature recently calculated within chiral perturbation theory. The obtained results on the QCD phase diagram for varying temperature, baryon chemical potential and magnetic field will be presented.
A principal element of unified description of strongly interacting matter within the effective theories corresponds to hadronization of chiral quark models and incorporation of the confinement mechanism into them, manifesting the switching between hadron and quark degrees of freedom. Such an approach is formulated based on a relativistic density-functional motivated by the string-flip model. Quasiparticle treatment of quarks provides their suppression due to the divergence of self-energy already at the mean-field level. Dynamical restoration of chiral symmetry is ensured by construction of the density functional. Beyond the mean field quark correlations in scalar and pseudoscalar channels are described within the Gaussian approximation. This explicitly introduces mesonic states into the model. Their contribution to the thermodynamic potential is analyzed within the Beth–Uhlenbeck framework. Modification of mesonic mass spectrum in the vicinity of (de)confinement is interpreted as the Mott transition.
The simulation-based inference is a powerful approach that can deal with various challenges ranging from discovering hidden properties to simulation algorithms tuning and optimising device configurations. Such methods as evolutionary algorithms or Bayesian optimisation usually help to address those challenges. However, those approaches rely on assumptions that might not hold. Recently, a series of methods have been introduced to estimate black-box gradients that significantly speed up the optimisation process. This talk outlines such methods: REINFORCE-based, variational optimisation and surrogate generative model-based approaches. We provide theoretical intuition for those methods as well as practical illustrations of their strengths and weaknesses. Such comparison will help practitioners to understand those methods and apply them to the inference tasks of their domains of interest.
Accurate and fast simulation of particle physics events is crucial for the high-energy physics community. Simulating particle interactions with the detector is both time consuming and computationally expensive. With its proton-proton collision energy of 13 TeV, the Large Hadron Collider is uniquely positioned to detect and measure the rare phenomena that can shape our knowledge of new interactions. The High-Luminosity Large Hadron Collider (HL-LHC) upgrade will put a significant strain on the computing infrastructure and budget due to increased event rate and levels of pile-up. The simulation of high-energy physics collisions needs to be significantly faster without sacrificing the physics accuracy. Modern machine learning approaches can offer faster solutions, while maintaining a high level of fidelity. We introduce a graph generative model that provides effective reconstruction of LHC events on the level of calorimeter deposits and tracks, paving the way for full detector level fast simulation.
In this talk, we introduce machine learning techniques for lattice QCD. Lattice QCD is one of the most successful methodologies of quantum field theory, which provides us quantitative values of QCD. On the other hand, machine learning enables us to treat big structured data. In particular, neural networks are widely used since it has universal approximation property while it cannot be exact. It seems that machine learning with lattice QCD is not match. We discuss exact ways to use machine learning in lattice QCD. Especially, we will introduce treatment of gauge symmetry in the neural network.