Coherent Exclusive $\rho^{0}$ Production in Ultra Peripheral Relativistic Heavy Ion Collisions with STAR

We present a measurement of the coherent $\rho^{0}$ and direct $\pi^{+}\pi^{-}$ pair photo-production in ultra peripheral relativistic heavy ion collisions at $\sqrt{s_{NN}}$=200 GeV. At impact parameters larger then twice the nuclear radius, the nuclei do not physically collide, but interact via long-range electromagnetic fields. The process $AuAu \rightarrow Au^{*}Au^{*}\rho^{0}$ with accompanying mutual nuclear excitations is observed. The transverse momentum of the $\rho^{0}$ is peaked at low $p_{T}$ which is consistent with coherent coupling to both nuclei. We report $\rho^{0}$ production cross section accompanied by mutual nuclear break-up and the ratio of direct pion to $\rho^{0}$ production.