Minijet Initial Conditions For Non-Equilibrium Parton Evolution at RHIC and LHC

Abstract

An important ingredient for the non-equilibrium evolution of partons at RHIC and LHC is to have some physically reasonable initial conditions for the single particle phase space distribution functions for the partons. We consider several plausible parametrizations of initial conditions for the single particle distribution function f_i(x,p) and fix the parameters by matching \int f(x,p)p^μd σ_μto the invariant momentum space semi-hard parton distributions obtained using perturbative QCD (pQCD), as well as fitting low order moments of the distribution function. We consider parametrizations of f_i(x,p) with both boost invariant and boost non-invariant assumptions. We determine the initial number density, energy density and the corresponding (effective) temperature of the minijet plasma at RHIC and LHC energies. For a boost non-invariant minijet phase-space distribution function we obtain ~ 30(140) /fm^3 as the initial number density, ~ 50(520) GeV/fm^3 as the initial energy density and ~ 520(930) MeV as the corresponding initial effective temperature at RHIC(LHC).