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

• Main Authors: Surrow, Bernd (Contributor), Balewski, Jan T. (Contributor), Betancourt, Michael Joseph (Contributor), Corliss, Ross Cameron (Contributor), Hays-Wehle, James Prewitt (Contributor), Hoffman, A. M. (Contributor), Jones, Christopher LaDon (Contributor), Kocoloski, Adam Philip (Contributor), Leight, William Axel (Contributor), Milner, Richard G. (Contributor), Redwine, Robert P. (Contributor), Sakuma, Tai (Contributor), Seele, Joseph Patrick (Contributor), van Nieuwenhuizen, Gerrit Jan (Contributor), Walker, M. (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor), Massachusetts Institute of Technology. Laboratory for Nuclear Science (Contributor)
• Format: Article
• Language: English
• Published: American Physical Society, 2010-08-10T20:21:40Z.
• Subjects: Article
• Online Access: Get fulltext

 We present a measurement of pi+pi-pi+pi-photonuclear production in ultraperipheral Au-Au collisions at [sqrt]sNN=200 GeV from the STAR experiment. The pi+pi-pi+pi- 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+pi-pi+pi- 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 pi+pi- final state and measure an upper limit for the ratio of the branching fractions of the ρ0(1700) to pi+pi- and pi+pi-pi+pi- 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.%.