Photoproduction of in ultraperipheral collisions at the BNL Relativistic Heavy Ion Collider
V. Guzey (National Research Center “Kurchatov Institute”, Petersburg Nuclear Physics Institute (PNPI), Gatchina 188300, Russia); E. Kryshen (National Research Center “Kurchatov Institute”, Petersburg Nuclear Physics Institute (PNPI), Gatchina 188300, Russia); M. Strikman (Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA); M. Zhalov (National Research Center “Kurchatov Institute”, Petersburg Nuclear Physics Institute (PNPI), Gatchina 188300, Russia)
We argue that the STAR data on photoproduction in ultraperipheral collisions (UPCs) at the momentum transfer primarily probes elastic and possibly nucleon-dissociative photoproduction on quasifree nucleons, while being essentially insensitive to expectedly weak nuclear modifications of the gluon distribution in the deuteron. Analyzing the STAR detector capabilities for selection of UPC events, we explore the possibility that the contribution of nucleon-dissociative photoproduction is negligibly small and obtain a very good description of the dependence of the STAR total cross section.
