SMuK 2021 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 22: Heavy-Ion Collisions and QCD Phases IV

HK 22.2: Talk

Thursday, September 2, 2021, 17:00–17:15, H1

Centrality and system size dependence of the thermal dilepton excess yield in HADES — •Niklas Schild for the HADES collaboration — TU Darmstadt, Darmstadt, Germany

Electromagnetic probes offer a unique opportunity to study the conditions in heavy-ion collisions throughout their whole evolution. In particular, the spectral shapes of dilepton distributions entail information about the temperature of the hot and dense fireball, while the integrated dilepton yield can be connected to the lifetime of the colliding system.

The collision centrality as well as the beam energy are arguably the two major determinants for the conditions reached in heavy-ion collisions. Less clear is the impact of the ion species or the spectator matter. For this reason, the HADES collaboration has recorded events for two collision systems at the same energy: Au+Au in April 2012 and Ag+Ag in March 2019, both at 1.23A GeV.

We present first results of the measured Ag+Ag thermal dilepton radiation and compare the extracted temperature of the fireball as well as the normalised excess yield to the measurements from Au+Au collisions.