Low-Mass Dileptons at the CERN-SpS: Evidence for Chiral Restoration?

TL;DR

This paper calculates dilepton production rates from hot, dense hadronic matter using an in-medium rho spectral function, providing evidence for chiral symmetry restoration at CERN-SpS energies.

Contribution

It offers a comprehensive in-medium rho spectral function constrained by experimental data, supporting the broadening scenario and its implications for chiral symmetry restoration.

Findings

Broadening of the rho resonance resembles perturbative qar{q} annihilation near the phase boundary.

Application to CERN-SpS Pb+Au collisions supports the broadening scenario.

Results suggest possible signals of chiral symmetry restoration.

Abstract

Using a rather complete description of the in-medium $\rho$ spectral function - being constrained by various independent experimental information - we calculate pertinent dilepton production rates from hot and dense hadronic matter. The strong broadening of the $\rho$ resonance entails a reminiscence to perturbative $q\bar q$ annihilation rates in the vicinity of the phase boundary. The application to dilepton observables in Pb(158AGeV)+Au collisions - incorporating recent information on the hadro-chemical composition at CERN-SpS energies - essentially supports the broadening scenario. Possible implications for the nature of chiral symmetry restoration are outlined.