Low mass dilepton production at ultrarelativistic energies

TL;DR

This study investigates low mass dilepton production in various high-energy nuclear collisions using a microscopic transport model, revealing that standard in-medium effects cannot fully explain the observed enhancements at RHIC energies.

Contribution

The paper applies the HSD transport approach to analyze dilepton production across different collision systems and energies, highlighting limitations of current in-medium effect models at RHIC.

Findings

Standard in-medium effects do not account for the large dilepton enhancement at RHIC.

The model reproduces data for lower-energy collisions but fails at higher energies.

In-medium modifications are insufficient to explain all observed dilepton yields.

Abstract

Dilepton production in $pp$ and $Au+Au$ nucleus-nucleus collisions at $\sqrt{s}$ = 200 GeV as well as in $In+In$ and $Pb+Au$ at 158 A$\cdot$GeV is studied within the microscopic HSD transport approach. A comparison to the data from the PHENIX Collaboration at RHIC shows that standard in-medium effects of the $\rho, \omega$ vector mesons - compatible with the NA60 data for $In+In$ at 158 A$\cdot$GeV and the CERES data for $Pb+Au$ at 158 A$\cdot$GeV - do not explain the large enhancement observed in the invariant mass regime from 0.2 to 0.5 GeV in $Au+Au$ collisions at $\sqrt{s}$ = 200 GeV relative to $pp$ collisions.