492 research outputs found
Coherent Vector Meson Production in Ultra-Peripheral Heavy-Ion Collisions at STAR
We report the first observation of coherent rho0 production (AuAu->AuAu rho0)
and rho0 production accompanied by mutual nuclear Coulomb excitation
(AuAu->Au*Au*rho0),and the observation of coherent e+e- pair production
(AuAu->Au*Au*e+e-) in ultra-peripheral relativistic heavy-ion collisions
(UPCs). We give transverse momentum, mass, and rapidity distributions. The
cross sections for coherent rho0 production at sqrt{s_NN}=130 and 200 GeV are
in agreement with theoretical predictions, which treat rho^0 production and
nuclear excitation as independent processes.Comment: 4 pages, 4 figures, Talk presented at Quark Matter 2002, Nantes,
France, July 200
Coherent Electromagnetic Processes in Ultra-Peripheral Heavy-Ion Collisions
We report measurements for coherent rho^0 production, AuAu->AuAu rho^0, and
coherent rho^0 and e^+e^- pair production accompanied by mutual nuclear Coulomb
excitation, AuAu->Au*Au* rho^0 and AuAuee, in ultra-peripheral relativistic
gold-gold collisions (UPC). We discuss transverse momentum, mass, and rapidity
distributions. The two photon-process of e^+e^- pair production is an important
probe of strong field QED because of the large coupling Z*alpha=0.6. At
sqrt{s}=200GeV, the e^+e^- production cross section agrees with lowest order
QED calculations. The cross sections for coherent rho^0 production at
sqrt{s}=130 and 200GeV are in agreement with theoretical predictions. The
calculations for both, coherent e^+e^- and rho^0 production treat nuclear
excitation as independent process.Comment: Presentation at the 'International Conference on the Structure and
Interactions of the Photon-Photon 2003, Frascati, Italy'; 6 pages, 8 figures
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