Coherent ρ0 production in ultraperipheral heavy-ion collisions

The STAR Collaboration reports the first observation of exclusive ρ 0 photoproduction, AuAu → AuAuρ 0 , and p° production accompanied by mutual nuclear Coulomb excitation, AuAu → Au*Au*ρ 0 , in ultraperipheral heavy-ion collisions. The p° have low transverse momenta, consistent with coherent coupling to both nuclei. The cross sections at √S N N = 130 GeV agree with theoretical predictions treating p° production and Coulomb excitation as independent processes.