Dielectron Continuum Production from $\sqrt{s_{NN}}$ = 200 GeV pp and Au+Au collisions at STAR

May 26, 2011, 3:40 PM
Salon Ravel AB (Imperial Palace)

Salon Ravel AB

Imperial Palace

Parallel Electromagnetic probes Electromagnetic probes




Dilepton distributions have been proposed as one of the penetrating probes for hot and dense nuclear matter created in high-energy nuclear collisions. Due to their relatively small final-state interaction cross-sections with the hot/dense environment, dileptons bring us direct information of the created matter in such collision. Since dileptons are created over all stages of heavy ion reactions, their sources vary as a function of kinematics. In the low mass region (LMR: mass<1.1GeV/$c^{2}$), dileptons are dominated by vector mesons and directed photons, while in the intermediate mass region (IMR: 1.1< mass< 3GeV/$c^{2}$) dileptons are dominated by thermal radiation of quark gluon plasma (QGP). In the high mass region (HMR: mass> 3 GeV/$c^{2}$), dileptons are mostly contributed by heavy (charm and bottom) quark decays and Drell-Yan processes. As a result, the dilepton distributions, especially in the IMR and HMR, could provide new aspects of early collision dynamics in heavy ion collisions. With the completion of the full barrel time-of-flight detector, the electron identification has been significantly improved at STAR, especially in low momentum region. In this talk we will present the first STAR results on dielectron production in p+p and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The results will be compared to hadron decay cocktails to search for vector meson in-medium modifications in LMR and the QGP thermal radiation in IMR. A systematic analysis of the transverse mass distributions in IMR region as a function of the mass in Au+Au collisions will be discussed. The results will be compared to those from 200 GeV p+p collisions as well as the results from SPS energies.

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