Erlangen 2026 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 41: Heavy-Ion Collisions and QCD Phases VII
HK 41.5: Talk
Thursday, March 19, 2026, 17:30–17:45, PHIL A 602
Combined description of thermal and vacuum contributions to the dilepton spectrum — •Jessica Vogel1, Tetyana Galatyuk1,2, Florian Seck1, and Joachim Stroth2,3 — 1Technische Universität Darmstadt — 2GSI, Darmstadt — 3Goethe-Universität Frankfurt
Dileptons give access to the hot and dense matter created in heavy-ion collisions, as they escape the reaction zone largely unaffected by strong interactions. Measurements of such penetrating probes provide insight into the properties of the created fireball. High baryon densities are reached at beam energies of a few GeV which lead to significant in-medium modifications on the spectral functions of vector mesons.
Because the short-lived ρ meson mainly decays inside the fireball, it primarily produces thermal dileptons. However, the longer-lived ω meson decays partly outside the fireball and thus contributes with a mix of thermal and vacuum rates to the dilepton spectrum.
This work introduces a framework that models the dilepton spectrum by describing the vacuum decays via the shining method and determines the thermal contribution using a coarse-graining microscopic transport approach. This joined approach gives accurate predictions of the invariant mass spectrum in collisions within the few GeV regime. We examine how the relative contribution of thermal and vacuum rates varies with transverse momentum and how the collision centrality influences the results.
This work has been supported by the DFG through grant CRC-TR 211.
Keywords: dilepton; hadronic matter; QGP; virtual photon