Non-equilibrium initial conditions from pQCD for RHIC and LHC

TL;DR

This paper calculates initial non-equilibrium conditions in heavy-ion collisions at RHIC and LHC energies using pQCD, emphasizing the impact of shadowing effects on particle production and initial temperature.

Contribution

It introduces a detailed analysis of shadowing effects on initial conditions in heavy-ion collisions using different gluon shadowing parametrizations.

Findings

Shadowing significantly affects particle multiplicities and energy production.

Different gluon shadowing ratios lead to markedly different initial temperature estimates.

Results highlight the importance of small-x parton distributions in collision modeling.

Abstract

We calculate the initial non-equilibrium conditions from perturbative QCD (pQCD) within Glauber multiple scattering theory for $\sqrt s =200$ AGeV and $\sqrt s =5.5$ ATeV. At the soon available collider energies one will particularly test the small $x$ region of the parton distributions entering the cross sections. Therefore shadowing effects, previously more or less unimportant, will lead to new effects on variables such as particle multiplicities $dN/dy$, transverse energy production $d\bar{E}_T/dy$, and the initial temperature $T_i$. In this paper we will have a closer look on the effects of shadowing by employing different parametrizations for the shadowing effect for valence quarks, sea quarks and gluons. Since the cross sections at midrapidity are dominated by processes involving gluons the amount of their depletion is particularly important. We will therefore have a closer look on the results for $dN/dy$, $d\bar{E}_T/dy$, and $T_i$ by using two different gluon shadowing ratios, differing strongly in size. As a matter of fact, the calculated quantities differ significantly.