Measurement of the helicity asymmetry in 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.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); George Washington Univ., Washington, DC (United States); Mississippi State Univ., Mississippi State, MS (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- Contributing Organization:
- The CLAS Collaboration
- Grant/Contract Number:
- AC05-06OR23177; SFB/TR110; 16-12-10267; SC0016583; FG02-07ER41528
- OSTI ID:
- 1416533
- Alternate ID(s):
- OSTI ID: 1416450; OSTI ID: 1439827
- Report Number(s):
- JLAB-PHY-17-2532; DOE/OR/23177-4227; arXiv:1708.02608; PRVCAN; TRN: US1800954
- Journal Information:
- Physical Review C, Vol. 96, Issue 6; ISSN 2469-9985
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Nucleon resonances in reaction
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journal | December 2019 |
Polarized ultrashort brilliant multi-GeV $γ$-rays via single-shot laser-electron interaction | text | January 2019 |
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