Recent Results Fromthe Ceres / Na 45 Experiment Andupgrade with a Radial - Drift
نویسنده
چکیده
The CERES/NA45 experiment measures low mass electron pair production in Pb-Au collisions at 158AGeV at the CERN SPS. In this paper, we present the electron pair enhancement in the mass range 0:2 < mee < 0:7 GeV/c 2 , it increases more than linear with charged multiplicity and is most pronounced at low pair pT < 0:5 GeV/c. Transverse mass and rapidity distributions for charged hadrons h + ? h ? and azimuthal event anisotropies (v1, v2) of charged particles are shown as a function of centrality. Finally, we present the status of the upgrade with a radial-drift TPC. 1. INTRODUCTION CERES is an experiment dedicated to the measurement of low-mass electron pair production in heavy-ion collisions at SPS energy. The production of dileptons is expected to convey information from the early stage of the collisions where quark-gluon-plasma (QGP) formation and restoration of chiral symmetry might happen. The CERES spectrometer is optimized to measure electron pairs from 50 MeV/c 2 up to 2 GeV/c 2 at mid-rapidity 2:1 < < 2:65 with 2 azimuthal coverage. The collision point (vertex) is determined by two silicon drift chambers (SDC) located just behind the target. Two ring imaging Cherenkov detectors (RICH) with methane gas radiator (th 32, which makes it blind to most of the hadrons) are used to identify electrons. A pad chamber (PC) 1
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تاریخ انتشار 2007