ρ0 photoproduction in ultraperipheral relativistic heavy ion collisions at √sNN=200 GeV

Abelev, B. I. and Planinić, Mirko and Poljak, Nikola and Zuo, J. X. (STAR Collaboration) (2008) ρ0 photoproduction in ultraperipheral relativistic heavy ion collisions at √sNN=200 GeV. Physical Review C, 77 (3). pp. 34910-11. ISSN 0556-2813

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Abstract

Photoproduction reactions occur when the electromagnetic field of a relativistic heavy ion interacts with another heavy ion. The STAR Collaboration presents a measurement of ρ^0 and direct π^+π^− photoproduction in ultraperipheral relativistic heavy ion collisions at √sNN=200 GeV. We observe both exclusive photoproduction and photoproduction accompanied by mutual Coulomb excitation. We find a coherent cross section of σ(AuAu→Au^∗Au^∗ρ^0)=530±19(stat.)±57(syst.) mb, in accord with theoretical calculations based on a Glauber approach, but considerably below the predictions of a color dipole model. The ρ^0 transverse momentum spectrum (p^2_T) is fit by a double exponential curve including both coherent and incoherent coupling to the target nucleus; we find σ_inc/σ_coh=0.29±0.03(stat.)±0.08(syst.). The ratio of direct π+π− to ρ^0 production is comparable to that observed in γp collisions at HERA and appears to be independent of photon energy. Finally, the measured ρ^0 spin helicity matrix elements agree within errors with the expected s-channel helicity conservation.

Item Type: Article
Keywords: photoproduction relativistic heavy ion collisions, time projection chamber, vector-meson production, diffractive production, proton scattering, complex nuclei, photon, Hera, colliders, energies, physics
Date: March 2008
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2008) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Project code: 119-0982887-1006
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 01 Jul 2014 10:58
Last Modified: 01 Jul 2014 10:58
URI: http://digre.pmf.unizg.hr/id/eprint/2347

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