Observation of pi+pi-pi+pi- photoproduction in ultraperipheral heavy-ion collisions at sqrt sNN = 200 GeV at the STAR detector

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We present a measurement of {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} photonuclear production in ultra-peripheral Au-Au collisions at {radical}s{sub NN} = 200 GeV from the STAR experiment. The {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} 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 {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} invariant mass spectrum of the coherent events exhibits a broad peak around 1540 {+-} 40 MeV/c{sup 2} with a width of 570 {+-} 60 MeV/c{sup 2}, ... continued below

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Collaboration, STAR & Abelev, Betty July 5, 2010.

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We present a measurement of {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} photonuclear production in ultra-peripheral Au-Au collisions at {radical}s{sub NN} = 200 GeV from the STAR experiment. The {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} 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 {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} invariant mass spectrum of the coherent events exhibits a broad peak around 1540 {+-} 40 MeV/c{sup 2} with a width of 570 {+-} 60 MeV/c{sup 2}, in agreement with the photoproduction data for the {rho}{sup 0}(1700). We do not observe a corresponding peak in the {pi}{sup +}{pi}{sup -} final state and measure an upper limit for the ratio of the branching fractions of the {rho}{sup 0}(1700) to {pi}{sup +}{pi}{sup -} and {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} of 2.5% at 90% confidence level. The ratio of {rho}{sup 0}(1700) and {rho}{sup 0}(770) coherent production cross sections is measured to be 13.4 {+-} 0.8{sub stat.} {+-} 4.4{sub syst.}%.

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  • Journal Name: Physical Review C

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  • Report No.: LBNL-3796E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 986227
  • Archival Resource Key: ark:/67531/metadc1012478

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • July 5, 2010

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  • Oct. 14, 2017, 8:36 a.m.

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  • Oct. 17, 2017, 6:23 p.m.

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Collaboration, STAR & Abelev, Betty. Observation of pi+pi-pi+pi- photoproduction in ultraperipheral heavy-ion collisions at sqrt sNN = 200 GeV at the STAR detector, article, July 5, 2010; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc1012478/: accessed June 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.