Observation of π+π−π+π− photoproduction in ultraperipheral heavy-ion collisions at √sNN=200 GeV at the STAR detector

Abelev, B. I. and Planinić, Mirko and Poljak, Nikola and Zoulkarneeva, Y. (STAR Collaboration) (2010) Observation of π+π−π+π− photoproduction in ultraperipheral heavy-ion collisions at √sNN=200 GeV at the STAR detector. Physical Review C, 81 (4). pp. 44901-9. ISSN 0556-2813

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Abstract

We present a measurement of π+π−π+π− photonuclear production in ultraperipheral Au−Au collisions at √sNN=200 GeV from the STAR experiment. The π+π−π+π− final states are observed at low transverse momentum and are accompanied by mutual nuclear excitation of the beam particles. The strong enhancement of the production cross section at low transverse momentum is consistent with coherent photoproduction. The π+π−π+π− invariant mass spectrum of the coherent events exhibits a broad peak around 1540±40 MeV/c2 with a width of 570±60 MeV/c2, in agreement with the photoproduction data for the ρ0(1700). We do not observe a corresponding peak in the π+π− final state and measure an upper limit for the ratio of the branching fractions of the ρ0(1700) to π+π− and π+π−π+π− of 2.5% at 90% confidence level. The ratio of ρ0(1700) and ρ0(770) coherent production cross sections is measured to be 13.4±0.8stat.±4.4syst.%.

Item Type: Article
Keywords: branching ratio, ratio, upper limit heavy ion, scattering gold peripheral pi, multiple production coherent interaction diffraction STAR mass spectrum, (2pi+ 2pi-) mass enhancement mass spectrum, (pi+ pi-) rho(1700), photoproduction rho(770)0, photoproduction cross section, ratio Brookhaven RHIC Coll rho(1700) --> 2pi+ 2pi- rho(1700) --> pi+ pi- 200 GeV-cms/nucleon
Date: April 2010
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2010) 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: 10 Jun 2014 09:13
Last Modified: 24 Feb 2016 15:35
URI: http://digre.pmf.unizg.hr/id/eprint/2318

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