$\rho^{0}$ Photoproduction in AuAu Collisions at $\sqrt{s_{NN}}$=62.4 GeV with STAR

TL;DR

This paper reports a measurement of coherent $ ho^0$ photoproduction cross section in AuAu collisions at 62.4 GeV, comparing it with higher energies and discussing implications for theoretical models.

Contribution

First measurement of $ ho^0$ photoproduction cross section at 62.4 GeV in heavy-ion collisions, providing data to test and refine theoretical predictions.

Findings

Cross section at 62.4 GeV is 10.5 mb with uncertainties.

Cross section ratio between 200 GeV and 62.4 GeV is 2.8.

Observed ratio is less than most theoretical model predictions.

Abstract

Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent $\rho^0$ photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent $\rho^0$ photoproduction with nuclear breakup is $10.5\pm1.5\pm 1.6$ mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is $2.8\pm0.6$, less than is predicted by most theoretical models. It is, however, proportionally much larger than the previously observed $15\pm 55$% increase between 130 GeV and 200 GeV.