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/dmdy(e+e−+Xn,y=0)=86±23(stat)±16(syst) μb/(GeV/c2) for me+e−∈[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.