Quark flavor equilibration of the quark-gluon plasma

Abstract

The early stage of a heavy-ion collision is marked by rapid entropy production and the transition from a gluon saturated initial condition to a plasma of quarks and gluons that evolves hydrodynamically. However, during the early times of the hydrodynamic evolution, the chemical composition of the QCD medium is still largely unknown. We present a study of quark chemical equilibration in the (Q)GP using a novel model of viscous hydrodynamic evolution in partial chemical equilibrium. Motivated by the success of gluon saturated initial condition models, we initialize the QCD medium as a completely gluon dominated state. Local quark production during the hydrodynamic phase is then simulated through the evolution of time-dependent fugacities for each independent quark flavor, with the timescales set as free parameters to compare different rates of equilibration. We present the results of complete heavy-ion collision simulations using this partial chemical equilibrium model, and show the effects on hadronic and electromagnetic observables. In particular, we show that the development of flow is sensitive to the equilibration timescale, providing an empirical way to probe the chemical equilibration of the QCD medium.

18 pages, 17 figures

References in corpus (11)

• The equation of state in (2+1)-flavor QCD
• The Color Glass Condensate
• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions
• The QCD Equation of State to $\mathcal{O}({\mu }_B^6)$ from Lattice QCD
• Phenomenological constraints on the transport properties of QCD matter with data-driven model averaging
• Transport Coefficients of Bulk Viscous Pressure in the 14-moment approximation
• Non-thermal p/pi ratio at LHC as a consequence of hadronic final state interactions
• Uniform description of bulk observables in the hydrokinetic model of A+A collisions at RHIC and LHC
• Thermalization of a color glass condensate and review of the "Bottom-Up" scenario
• Modified equilibrium distributions for Cooper--Frye particlization