Heavy quark diffusion in a Polyakov loop plasma

Abstract

We calculate the transport coefficients, drag and momentum diffusion, of a heavy quark in a thermalized plasma of light quarks in the background of Polyakov loop. Quark thermal mass and the gluon Debye mass are calculated in a non-trivial Polyakov loop background. The constituent quark masses and the Polyakov loop is estimated within a Polyakov loop quark meson (PQM) model. The relavant scattering amplitudes for heavy quark and light partons in the background of Polyakov loop has been estimated within the matrix model. We have also compared the results with the Polyakov loop parameter estimated from lattice QCD simulations. We have studied the temperature and momentum dependence of heavy quark drag and diffusion coefficients. It is observed that the temperature dependence of the drag coefficient is quite weak which may play a key role to understand heavy quark observables at RHIC and LHC energies. I. INTRODUCTIONExperimental heavy-ion collision (HIC) programs at Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) indicate the production of a liquid-like phase of the matter, having a remarkably small value of shear viscosity to entropy density ratio, η/s ≈ 0.1, where the properties of the system are governed by quarks and gluons. Such a state of matter is known as quark gluon plasma (QGP) [1,2]. To characterize the properties of QGP, penetrating and well calibrated probes are essential. In this context, the heavy quarks (HQs) [3][4][5][6][7][8][9], mainly charm and bottom, play a crucial role since they do not constitute the bulk part of the matter owing to their larger mass compared to the temperature created in heavy-ion collisions. Also, thermal production of heavy quarks is negligible, due to their large masses, in the QGP within the range of temperatures that can be achieved in RHIC and LHC colliding energies.Heavy quarks are exclusively created in hard processes which can be handled by perturbative QCD calculations [10], and therefore, their initial distribution is theoretically known and can be verified by experiment. They interact with the plasma constituents, the light quarks, and the gluons, but their initial spectrum is too hard to come to equilibrium with the medium. Therefore, the high momentum heavy quarks spectrum carry the information of their interaction with the plasma particles during the expansion of the hot and dense fireball and on the plasma properties. Since the light quark, anti-quark and gluons are thermalized, the heavy quark interaction with the light constituents leads to a Brownian motion which can be treated with the framework of a Fokker Plank equation. Thus the interaction of the heavy quark in QGP is contained in the drag and diffusion coefficients of the heavy quark. The resulting momentum distribution of the heavy mesons which depend upon the drag and diffusion coefficients get reflected in the nuclear modification factor (R AA ) which is measured experimentally.Initially, pQCD predicted a small nuclear suppression factor [11,12], R AA , in nucleus-nucl...

Nonperturbative effects on radiative energy loss of heavy quarks

“…For all cases, a markedly different feature from the standard pQCD approach are the rather large thermal-parton masses dictated by the constraints from the QGP EoS and microscopically related to the Polyakov loop encoding the nontrivial information of the confinement [36] JHEP08(2020)168 generated selfconsistently from the confining potential. Similar features from including effects of the Polyakov loop have recently been found from a different perspective, within the Polyakov-quark-meson model [47]. With a gluon mass of around 1 GeV at low temperature, soft radiation is heavily suppressed.…”

Non-extensive Boltzmann Transport Equation: the Relaxation Time Approximation and Beyond

“…We have taken q = 1.01, and temperature to be 350 MeV (for Figs. 5,7,9), and momentum of the energetic light quark to be 5 GeV (for Figs. 6,8,10).…”

“…Since then, it has been used in many fields including that of high energy collisions. For example, to understand the transport of particles inside the quark-gluon plasma medium produced in high energy collisions, either the BTE, or some approximated version of it has been used [2][3][4][5][6][7][8]. In this approach, the evolution of a distribution function is studied, and is utilized to understand the observables in the multi-particle production experiments colliding protons or heavy-ions.…”

Thermoelectric transport coefficients of quark matter

“…However, this has been attempted with the relax-ation time estimated within perturbative QCD which may be valid for asymptotically high temperatures. Further, it ought to be mentioned that, the vacuum structure of QCD remain nontrivial near the critical temperature region with nonvanishing values for the quark-antiquark condensates associated with chiral symmetry breaking as well as Polyakov loop condensates associated with the physics of statistical confinement [77][78][79][80]. Indeed, within the ambit of the NJL model, it was shown that the temperature dependence of viscosity coefficients exhibits interesting behavior of phase transition with the shear viscosity to entropy ratio showing a minimum while the coefficient of bulk viscosity showing a maximum at the phase transition [77,78,81].…”