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HK: Fachverband Physik der Hadronen und Kerne

HK 13: Physik mit schweren Ionen

HK 13.6: Talk

Monday, March 10, 2008, 18:00–18:15, 2E

Centrality dependence of proton and antiproton yields in Pb+Pb collisions at √s_NN=17.3 GeV — Hans Beck¹, Julian Book¹, Christoph Blume¹, Peter Dinkelaker¹, Volker Friese², Marek Gazdzicki¹, Claudia Höhne², Dmytro Kresan², Benjamin Lungwitz¹, Michael Mitrovski¹, Rainer Renfordt¹, Tim Schuster¹, Reinhard Stock¹, Claudia Strabel¹, Herbert Ströbele^1,2, •Milica Utvic¹, and Alexander Wetzler¹ for the NA49 collaboration — ¹Fachbereich Physik der Universität Frankfurt — ²Gesellschaft für Schwerionenforschung (GSI), Darmstadt

The centrality dependence of proton and antiproton spectra in high energy nuclear collisions is used to study the evolution of baryon stopping and transverse flow with the volume of interacting matter. The (anti −) proton yields in Pb+Pb minimum bias collisions at √s_NN=17.3 GeV were measured by the NA49 Collaboration. They were identified in the c.m. rapidity interval -0.4 < y < 1.0 (corresponding to the laboratory momentum range 5-40 GeV/c) via their specific energy loss in the TPC detector gas. The resulting raw yields were corrected for geometrical acceptance, reconstruction efficiency and feeddown from weak decays. Rapidity distributions, transverse mass spectra and inverse slope parameters were studied as a function of collision centrality and compared to published data. It is found that the ratio of antiprotons to protons at midrapidity increases approximately by a factor of 2 from peripheral to the most central collisons.