Speaker
Description
At the ALICE experiment at CERN, quark-gluon plasma (QGP) is produced in the early stages of ultra-relativistic heavy ion collisions. Prior to the formation of QGP, heavy quarks and antiquarks (charm and beauty) are created in the initial hard scattering of the partons of the heavy ions. They subsequently move through the QGP, their numbers remaining conserved while they interact with the hot and dense medium. Thus, the QGP can be studied by comparing hadron spectra from heavy ion collisions to corresponding reference spectra from proton-proton collisions, where no QGP is expected. Such comparisons, at RHIC and LHC energies, show a suppression of most hadronic probes -- an observation that is interpreted as a signature of energy loss through interaction of the quarks with other free colour charges, and therefore indicative of QGP formation.
Light quarks in hadronic probes can be produced later in the collision, but the heavy beauty quark is almost exclusively formed in the initial parton collisions. Beauty quarks thus experience the full history of the collision. The open beauty hadrons formed through combining with lighter quarks are likely to carry the kinematics of the beauty quark and reflect the beauty specific energy loss. Therefore the B meson ($b \bar{q}$, $\bar{b} q$, where $q$ is a light quark) is particularly well-suited as a probe to the QGP. However, the $B$ meson is difficult to study due to its many-prong decay topologies and the low production rate of the beauty quarks. In this talk I will present plans to use the $B \rightarrow J/\psi + K$ decay channel to probe the QGP, taking advantage of the low noise of the dilepton decay channel of $J/\psi$ and the analysis framework developed for this channel at the ALICE-Oslo group. The non-prompt $J/\psi$ mesons will have a displaced vertex with respect to the primary vertex. The upgrade of the Inner Tracking System of ALICE will improve the vertex determination capabilities and have a large impact on the precision of this measurement. This upgrade, combined with the increased statistics expected from LHC run 3, makes the reconstruction of B mesons as a probe to the QGP a feasible approach.
