Heidelberg 2015 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 73: Heavy Ion Collisions and QCD Phases 10
HK 73.1: Gruppenbericht
Freitag, 27. März 2015, 14:30–15:00, T/HS2
Low-Mass Dielectron Measurements in pp, p–Pb and Pb–Pb Collisions with ALICE — •Mahmut Özdemir for the ALICE collaboration — Institut für Kernphysik, Goethe-Universität Frankfurt
Low-mass dielectrons are an important experimental tool to investigate the properties of strongly interacting matter, in particular the quark-gluon plasma (QGP), which is created in ultrarelativistic heavy-ion collisions. Electrons do not interact strongly, therefore they provide information from all stages of the collision. Especially, possible modifications of the electromagnetic emission spectrum in the QGP can be probed with dielectrons, where pp collisions are used as medium-free reference and p–A collisions allow to probe cold from hot nuclear matter effects.
In this contribution, dielectron measurements in ALICE are presented, where electrons at mid-rapidity are identified by their specific energy loss in the Inner Tracking System (ITS) and the Time Projection Chamber, combined with time-of-flight information from the TOF detector. The invariant mass distributions in pp collisions at √s = 7 TeV and in p–Pb collisions at √sNN = 5.02 TeV are compared to the expected hadronic sources. Moreover, the cross section of virtual direct photons measured in pp collisions is compared to predictions from NLO calculations as a function of the transverse momentum. Also the status of the analysis of Pb–Pb collisions at √sNN = 2.76 TeV is presented.