Abstract
The bulk viscosity of thermalized QCD matter at temperatures above a few hundred MeV could be significantly influenced by charm quarks because their contribution arises four perturbative orders before purely gluonic effects. In an attempt to clarify the challenges of a lattice study, we determine the relevant imaginary-time correlator (of massive scalar densities) up to NLO in perturbation theory, and compare with existing data. We find discrepancies much larger than in the vector channel; this may hint, apart from the importance of taking a continuum limit, to larger non-perturbative effects in the scalar channel. We also recall how a transport peak related to the scalar density spectral function encodes non-perturbative information concerning the charm quark chemical equilibration rate close to equilibrium.
Highlights
The physical processes relevant for the bulk viscosity are those associated with the breaking of scale invariance
We recall how a transport peak related to the scalar density spectral function encodes non-perturbative information concerning the charm quark chemical equilibration rate close to equilibrium
The purpose of this paper has been to investigate the influence of a finite charm quark mass on a 2-point imaginary-time correlator in the so-called bulk channel, corresponding to the trace of the energy-momentum tensor in continuum QCD
Summary
The expectation value in eq (2.4) vanishes in the chiral limit Mi ≪ πT and, because of Boltzmann suppression, for large masses, Mi ≫ πT It can give a rather substantial contribution for Mi ∼ πT ; for temperatures relevant for heavy ion collision experiments, this could be the case with charm quarks [31]–[34], which have a mass Mc < MD0 = 1.86 GeV. If Γchem > ω, a hydrodynamical description applies and the heavy quark contribution should be added to the bulk viscosity. In each case the chemical equilibration rate Γchem is seen to be a fundamental quantity, whose non-perturbative determination as a function of the heavy quark mass would be more than welcome
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
