Berlin 2005 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 18: Physik mit schweren Ionen

HK 18.4: Vortrag

Montag, 7. März 2005, 15:15–15:30, TU MA041

Universal behaviour of the nuclear modification factor at RHIC ? — •Jörn Putschke — Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München

Measurements of the nuclear modfication factor R_dAu (and R_CP) and back-to-back correlations at high p_T at mid-rapidity from d+Au collisions at RHIC at √s_NN = 200 GeV demonstrated, that the strong supression of high p_T particle production previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions [1]. Recent results of the pseudorapidity and centrality dependence of R_dAu (and R_CP) from the BRAHMS collaboration [2] were interpreted as a possible onset of parton saturation in the Color Glass Condensate [3].

An alternative explanation of the strong supression of R_dAu (and R_CP) at forward rapidities will be presented. In this Ansatz the supression at higher rapidities is explained by the supression of particle yields in d+Au relative to p+p collisions caused by a shift of the center of mass in the asymmetric d+Au collisions with respect to the nucleon-nucleon center of mass system.

In this new reference system the pseudorapidity and centrality dependence of R_dAu (and R_CP) can be explained and taking the asymmetry into account R_dAu (and R_CP) show a universal behaviour at RHIC energies.

[1] J. Adams, et al., Phys.Rev.Lett., 91:072304, 2003

[2] I. Arsene et al., arXiv:nucl-ex/0403005

[3] D. Kharzeev, E. Levin, and M. Nardi, Nucl. Phys. A, 730:448, 2004