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

The collaboration
Phys.Rev.C 85 (2012) 014910, 2012.

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.

• Figure 1 (left)

Data from Figure 1, left pannel

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Acceptance corrected invariant mass distributions for the coherently produced $\rho^0$ candidates collected with trigger A (left) and B (right). The...

• Figure 1 (right)

Data from Figure 1, right pannel

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Acceptance corrected invariant mass distributions for the coherently produced $\rho^0$ candidates collected with trigger A (left) and B (right). The...

• Figure 2

Data from Figure 2

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Transverse momentum distribution of the $\rho^0$ candidates (open distribution) overlaid by the combinatorial background estimated with like-sign pairs (not corrected...

• Figure 3

Data from Figure 3

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$\rho^0$ production cross section determined with the data set collected with trigger B, as a function of momentum transfer $t$,...

• Figure 4

Data from Figure 4

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Comparison of theoretical predictions to the measured total cross section for coherent $\rho^0$ production as a functionof $\sqrt{s_{NN}}$ . The...