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

Scientific paper - Original scientific paper

• Author: B. I. Abelev
• Author: ...
• Author: Mirko Planinić
• Author: ...
• Author: Nikola Poljak
• Author: ...
• Author: J. X. Zuo
• Collaboration: STAR Collaboration
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

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.

• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review C - Nuclear Physics
• Numbering: vol. 77, no. 3, 034910
• p-ISSN: 0556-2813
• e-ISSN: 1089-490X
• DOI: https://doi.org/10.1103/PhysRevC.77.034910
• URN:NBN: urn:nbn:hr:217:269837
• Publication: 2008
• Project: Number: 119-0982887-1006; Title (croatian): Istraživanje hadronskih sustava upotrebom relativističkih projektila; Leader: Mirko Planinić; Jurisdiction: Croatia; Funding stream: ZP
• Document URL: http://link.aps.org/doi/10.1103/PhysRevC.77.034910
• Type of resource: Text
• Access conditions: Open access
• Public note: Copyright (2008) by the American Physical Society. Received 21 December 2007; published 31 March 2008.
• Created on: 2019-10-18 21:10:07