Dilepton Signature of a First-Order Phase Transition

TL;DR

This paper investigates dilepton radiation as a potential signature of a first-order phase transition in QCD matter created in heavy-ion collisions, using hydrodynamic simulations with different equations of state.

Contribution

It introduces a hydrodynamic model with two equations of state to identify dilepton signatures indicative of a first-order phase transition in QCD.

Findings

First-order transition increases low-mass thermal dilepton emission by about a factor of two.

The study constrains equations of state using lattice QCD and neutron star data.

Latent heat significantly impacts dilepton emission signals.

Abstract

The search for a first-order phase transition in strongly interacting matter is one of the major objectives in the exploration of the phase diagram of Quantum Chromodynamics (QCD). In the present work we investigate dilepton radiation from the hot and dense fireballs created in Au-Au collisions at projectile energies of 1-2 $A$GeV for potential signatures of a first-order transition. Toward this end, we employ a hydrodynamic simulation with two different equations of state, with and without a phase transition. The latter is constrained by susceptibilities at vanishing chemical potential from lattice-QCD as well as neutron star properties, while the former is implemented via modification of the mean-fields in the quark phase. We find that the latent heat involved in the first-order transition leads to a substantial increase in the low-mass thermal emission signal, by about a factor of two above the cross-over scenario.