Thursday, February 2, 2012

1107.4630 (G. Agakishiev et al.)

$ρ^{0}$ Photoproduction in AuAu Collisions at $\sqrt{s_{NN}}$=62.4
GeV with STAR
   [PDF]

G. Agakishiev, for the STAR Collaboration
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.
View original: http://arxiv.org/abs/1107.4630

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