Heidelberg 2015 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 64: Heavy Ion Collisions and QCD Phases 8
HK 64.3: Gruppenbericht
Donnerstag, 26. März 2015, 18:00–18:30, T/HS1
First results on electromagnetic radiation from Au+Au collisions at Ebeam=1.23 GeV/u in HADES. — •Szymon Harabasz for the HADES collaboration — TU Darmstadt
Investigations of heavy-ion collisions at low beam energies do not only reveal properties of vector mesons and baryonic resonances in hot/dense hadronic matter, but they also give access to the thermodynamics of QCD in the low T and high µB region of the phase diagram. Electromagnetic radiation emitted from such collisions provides a unique chance to study these issues in the laboratory. As photons and leptons are not subject to the strong force, they are able to deliver nearly undisturbed information on the processes in which they were produced. The High Acceptance Di-Electron Spectrometer installed at GSI has been used since many years to take these opportunities and study a wide range of colliding systems from NN and π N through NA to AA, including the Au+Au at Ebeam=1.23 GeV/u run from April-May 2012. Here, according to the non-linear scaling ∝ Apart1.4 extracted from the former C+C and Ar+KCl results, much stronger in-medium radiation is expected.
In the current contribution, very non-trivial questions of e+e− identification, rejection of the strong contribution of γ-conversion and a proper treatment of combinatorics in such a background-dominated system will be addressed. A discussion of the obtained results on dilepton spectra will then follow.
This work has been supported by VH-NG-823, Helmholtz Alliance HA216/EMMI, GSI, HGS-HIRe and H-QM.