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Title: Measurement of the helicity asymmetry E in ω π + π - π 0 photoproduction

The double-polarization observable $E$ was studied for the reaction $$\gamma p\to p\omega$$ using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally-polarized frozen-spin target (FROST). The observable was measured from the charged decay mode of the meson, $$\omega\to\pi^+\pi^-\pi^0$$, using a circularly-polarized tagged-photon beam with energies ranging from the $$\omega$$ threshold at 1.1 to 2.3 GeV. A partial-wave analysis within the Bonn-Gatchina framework found dominant contributions from the $3/2^+$ partial wave near threshold, which is identified with the sub-threshold $$N(1720)\,3/2^+$$ nucleon resonance. To describe the entire data set, which consisted of $$\omega$$ differential cross sections and a large variety of polarization observables, further contributions from other nucleon resonances were found to be necessary. Here, with respect to non-resonant mechanisms, $$\pi$$ exchange in the $t$-channel was found to remain small across the analyzed energy range, while pomeron $t$-channel exchange gradually grew from the reaction threshold to dominate all other contributions above $$W \approx 2$$ GeV.
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Publication Date:
Report Number(s):
JLAB-PHY-17-2532; DOE/OR/23177-4227; arXiv:1708.02608
Journal ID: ISSN 2469-9985; PRVCAN; TRN: US1800954
Grant/Contract Number:
AC05-06OR23177; SFB/TR110; 16-12-10267; SC0016583
Type:
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 96; Journal Issue: 6; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); George Washington Univ., Washington, DC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
The CLAS Collaboration
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; meson photoproduction
OSTI Identifier:
1416533
Alternate Identifier(s):
OSTI ID: 1416450; OSTI ID: 1439827