Köln 2004 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 7: Heavy Ions I
HK 7.10: Vortrag
Montag, 8. März 2004, 18:30–18:45, F
Multiphoton Exchange Processes in Ultraperipheral Relativistic Heavy Ion Collisions — •Kai Hencken1, Gerhard Baur2, Andreas Aste1, Dirk Trautmann1, Spencer Klein3, and Ute Dreyer1 — 1Universität Basel, Switzerland — 2Forschungszentrum Jülich, Germany — 3Lawrence Berkeley National Laboratory, USA
The very strong electromagnetic fields present in relativistic heavy ion collisions allow to study photonuclear and photon-photon reactions in ultraperipheral collisions (UPC) at RHIC and the LHC with energies beyond what has been possible at HERA. Among them is the coherent production of vector mesons (up to the Upsilon), a most important QCD process [1]. Due to the strong field also higher order processes are possible and have been used, e.g, as a trigger for UPCs [2]. We study these multiphoton exchange processes in both perturbation theory and Glauber approximation. Factorization of the multi-photon amplitudes into independent single-photon amplitudes is found to be a good approximation in many cases [3]. Due to the common impact parameter vector, correlations in b are found. We discuss cases, where these correlations can be detected. As a special case we calculate the cross section for e+e− pair production together with GDR excitation of both ions [4], a process, which was measured by STAR [5]. ([1] G. Baur et al., Physics Reports 364 (2002) 359. [2] C. Adler et al., PRL89, 272302 (2002). [3] G. Baur et al., NPA729, 787 (2003). [4] K. Hencken et al., in preparation (2003). [5] S. Klein for the STAR Collaboration, nucl-ex/0310020.)