Duality and Chiral Restoration from Dilepton Production in Relativistic Heavy-Ion Collisions

TL;DR

This paper reviews the theoretical understanding of dilepton production in high-energy heavy-ion collisions, highlighting how in-medium modifications of vector mesons and thermal radiation explain experimental enhancements.

Contribution

It provides a comprehensive analysis of dilepton production mechanisms, emphasizing the role of vector meson broadening and chiral symmetry restoration in hot and dense matter.

Findings

Broadening of vector mesons in hot/dense matter explains low-mass dilepton enhancement.

Thermal radiation accounts for intermediate-mass dilepton excess.

Consistent description aligns with experimental data from CERN-SpS energies.

Abstract

We discuss the recent status in the theoretical understanding of dilepton production in central heavy-ion reactions with the Pb-beam at the full CERN-SpS energy of 158 AGeV. In the low-mass region ($M\le$~1 GeV) a strong broadening of the vector meson resonances in hot and dense matter (especially for the $\rho$ meson) entails thermal dilepton rates very reminiscent to perturbative $q\bar q$ annihilation close to the expected phase boundary of the chiral symmetry restoring transition. A consistent description of the experimentally observed enhancement at both low and intermediate masses (1.5 GeV~$\le M \le$~3 GeV) in terms of thermal radiation from an expanding fireball can be obtained.