Dilepton production from parton interactions in the early stage of relativistic heavy-ion collisions

TL;DR

This paper investigates dilepton production in early-stage relativistic heavy-ion collisions using a transport model that incorporates off-shell parton interactions based on lattice QCD results, highlighting the significance of partonic channels.

Contribution

It introduces off-shell cross sections for partonic dilepton production derived from the DQPM and implements them into the PHSD model to analyze experimental data.

Findings

Partonic channels significantly contribute to dilepton yields in certain phase space regions.

The model reproduces experimental dilepton spectra from NA60 and PHENIX.

Off-shell effects are crucial for accurate dilepton production modeling.

Abstract

We address the dilepton production from the parton interactions in the early stage of relativistic heavy-ion collisions within the parton-hadron-string dynamics (PHSD) off-shell transport approach. The description of partons in PHSD is based on the dynamical quasiparticle model (DQPM) matched to reproduce lattice QCD results in thermodynamic equilibrium. According to the DQPM the constituents of the strongly interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles (quarks and gluons) with broad spectral functions. In order to address the electromagnetic radiation of the sQGP, we derive off-shell cross sections of q+qbar->gamma*, q+qbar->gamma*+g and q+g->gamma*+q (qbar+g->gamma*+qbar) reactions taking into account the effective propagators for quarks and gluons from the DQPM. Dilepton production in In+In collisions at 158 AGeV and in Au+Au at sqrt(s)=200 GeV is calculated by implementing these off-shell processes into the PHSD transport approach. By comparing to the data of the NA60 and PHENIX Collaborations, we study the relative importance of different dilepton production mechanisms and point out the regions in phase space where partonic channels are dominant.