Coherent Photon-Pomeron and Photon-Photon Interactions in Ultra-Peripheral Collisions at RHIC

Abstract

Ultra-peripheral heavy ion collisions involve long range electromagnetic interactions at impact parameters larger than twice the nuclear radius, where no nucleon-nucleon collisions occur. The first observation of coherent rho^0 production with and without accompanying nuclear breakup, AuAu->Au*Au*rho^0 and AuAu->Au Au rho^0 respectively, and the observation of e+e- pair production AuAu->Au*Au*e+e- are presented by the STAR collaboration. The transverse momentum spectra are peaked at low pT, showing the coherent coupling to the nuclei. A clear rho^0 signal is observed in the two pion invariant mass spectrum.

Proceedings Photon 2001, Ascona Switzerland, 2.-7. Sep. 2001 4 pages, 6 figures