Minijet initial conditions for non-equilibrium parton evolution at RHIC and LHC

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 fi(x,p) and fix the parameters by matching ∫f(x,p)pμ dσμ to 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 fi(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)/fm3 as the initial number density, ∼50(520) GeV/fm3 as the initial energy density and ∼520(930) MeV as the corresponding initial effective temperature at RHIC(LHC).