  Ultra-peripheral collisions (UPC) of heavy-ions involve long range
electromagnetic interactions at impact parameters twice larger than the nuclear
radius, where no nucleon-nucleon collisions occur. The first measurement of
photoproduction of $J/\psi$ and of two-photon production of high-mass $e^+ e^-$
pairs in ultra-peripheral nucleus-nucleus interactions will be presented, using
Au+Au data at $\sqrt{s_{_{NN}}}$ = 200 GeV. The measured cross sections at
midrapidity are consistent with various theoretical predictions.

Nuclear Experiment