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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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.
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...
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...
