Photoproduction of omega with linearly polarized photons at CLAS

Conference · Mon Oct 01 04:00:00 EDT 2007

OSTI ID:1967352

Cheng, Lu ^[1]; Klein, Franz ^[1]

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1. Catholic University of America

The CLAS-g8 running period with linearly polarized photons allowed for the extracton of beam and parity asymmetry for the omega-p channel at photon energies between threshold and 2.1 GeV. Although our analysis aims for providing tight constraints on baryon resonances decaying into omega-N, a by-product is the separation of contributions of natural and unnatural parity- exchange mechanisms. Such a measurement is considered as an important step to parametrize the t-channel background for resonant production. The vector meson is identified in the decay mode omega --> pi+ pi- pi0. The recoil proton was detected in coincidence with two charged pions and the missing pi0 identified via missing mass. The three-pion mass spectrum shows a strong omega signal that is enhanced in the forward direction as expected from diffractive and pion-exchange processes. The extracted spin density matrix elements confirm the dominating pion-exchange mechanism for the lower energy points. However, the (preliminary) cross section and asymmetries are not fully consistent with t-channel processes: the cross section enhancement at cos theta_cm ~ 90 deg. and the modulation of the angular distribution of the decay pions indicate the presence of resonant production.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1967352
• Report Number(s): JLAB-PHY-07-978; DOE/OR/23177-5936
• Country of Publication: United States
• Language: English