Dilepton production in proton-proton and Pb+Pb collisions at sqrt(s_NN)=2.76 TeV

TL;DR

This paper compares two models, SHM and PHSD, to study dilepton production in proton-proton and Pb+Pb collisions at 2.76 TeV, revealing insights into in-medium rho-meson modifications and partonic contributions.

Contribution

It provides a detailed comparison of statistical and transport models for dilepton production at LHC energies, highlighting the role of partonic phases and in-medium effects.

Findings

PHSD roughly agrees with hadronic dilepton spectra

In-medium rho-meson modification increases low mass dileptons

Partonic degrees of freedom dominate intermediate mass dilepton production

Abstract

We study e^+e^- pair production in proton-proton and central Pb+Pb collisions at sqrt(s_NN)=2.76 TeV within two models: an extended statistical hadronization model (SHM) and the Parton-Hadron-String Dynamics (PHSD) transport approach. We find that the PHSD calculations roughly agree with the dilepton spectrum from hadronic sources with the 'cocktail' estimates from the statistical hadronization model matched to available data at LHC energies. The dynamical simulations within the PHSD show a moderate increase of the low mass dilepton yield essentially due to the in-medium modification of the rho-meson. Furthermore, pronounced traces of the partonic degrees of freedom are found in the PHSD results in the intermediate mass regime. The dilepton production from the strongly interacting quark-gluon plasma (sQGP) exceeds that from the semi-leptonic decays of open charm and bottom mesons. Additionally, we observe that a transverse momentum cut of 1 GeV/c further suppresses the relative contribution of the heavy meson decays to the dilepton yield, such that the sQGP radiation strongly dominates the spectrum for masses from 1 to 3 GeV, allowing a closer look at the electromagnetic emissivity of the partonic plasma in the early phase of Pb+Pb collisions.