Measurement of Mutual Coulomb Dissociation in $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\mathrm{GeV}$ $Au+Au$ Collisions

We report on the first measurement of mutual Coulomb dissociation in heavy-ion collisions. We employ forward calorimeters to measure neutron multiplicity at beam rapidity. The cross section for simultaneous electromagnetic breakup of Au nuclei at a nucleon-nucleon center of mass energy $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\mathrm{GeV}$ is ${\sigma }_{\mathrm{MCD}}=3.67\mathrm{}\pm 0.26$ barns, which is comparable to the geometrical cross section. The ratio of the electromagnetic to the total cross section is in good agreement with calculations, as is the neutron multiplicity distribution.