Photoproduction of J/ψ and of High Mass e+e- in Ultra-Peripheral Au+Au Collisions at √sNN = 200 GeV

We present the first measurement of photoproduction of J/ψ and of two-photon production of high-mass e+e- pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au + Au data at √sNN = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au* nuclei. The event sample consists of 28 events with me+e+ > 2 GeV/c2 with zero like-sign background. The measured cross sections at midrapidity of dσ/dy (J/ψ + Xn,y = 0) = 76 ± 33(stat) ± 11(syst) μb and d2σ/dm dy(e+e- + Xn, y = 0) = 86 ± 23(stat) ± 16(syst) μb/(GeV/c2) for me+e- (elementof) (2.0,2.8) GeV/c2 have been compared and found to be consistent with models for photoproduction of J/ψ and QED based calculations of two-photon production of e+e- pairs.