Thermal dileptons as QCD matter probes at SIS

TL;DR

This paper investigates how thermal dileptons emitted during heavy-ion collisions at SIS energies can serve as probes for the properties of hot and dense QCD matter, using a coarse-graining approach to model the collision evolution.

Contribution

It introduces a coarse-graining method to connect transport simulations with thermal dilepton emission based on an in-medium rho spectral function at SIS energies.

Findings

Provides an excitation function of thermal excess radiation.

Establishes a baseline for future experimental measurements.

Connects transport models with electromagnetic probes of QCD matter.

Abstract

Electromagnetic radiation is emitted during the whole course of a heavy-ion collision and can escape from the collision zone without further interactions. This makes it an ideal tool to study the properties of hot and dense QCD matter. To model the space-time evolution of the collision at SIS energies a coarse-graining approach is used to convert transport simulations into meaningful temperatures and densities. These parameters serve as input for the determination of the pertinent radiation of thermal dileptons based on an in-medium $\rho$ spectral function that describes available spectra at ultrarelativistic collision energies. The resulting excitation function of the thermal excess radiation provides a baseline for future measurements by the HADES and CBM experiments at GSI/FAIR, and experiments proposed at NICA and J-PARC.