Can transport peak explain the low-mass enhancement of dileptons at RHIC?

TL;DR

This paper links the low-mass dilepton enhancement at RHIC to the transport properties of the quark-gluon plasma, using a novel spectral function approach combined with hydrodynamics and lattice QCD data.

Contribution

It introduces a new relation between dilepton enhancement and QGP transport coefficients using a spectral function parameterization within relativistic hydrodynamics.

Findings

The low-mass dilepton enhancement mainly originates from the high-temperature QGP phase.

The spectral function parameterization aligns well with experimental data.

Charge fluctuations from lattice QCD are consistent with the observed enhancement.

Abstract

We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant $D$ and the relaxation time $\tau_{\rm J}$. We parameterize the transport peak in the spectral function using the second-order relativistic dissipative hydrodynamics by Israel and Stewart. Combining the spectral function and the full (3+1)-dimensional hydrodynamical evolution with the lattice EoS, theoretical dielectron spectra and the experimental data are compared. Detailed analysis suggests that the low-mass dilepton enhancement originates mainly from the high-temperature QGP phase where there is a large electric charge fluctuation as obtained from lattice QCD simulations.