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Title: Measurement of the generalized form factors near threshold via γ *p → nπ + at high Q 2

We report the first extraction of the pion-nucleon multipoles near the production threshold for the nπ + channel at relatively high momentum transfer (Q 2 up to 4.2 GeV 2). The dominance of the s-wave transverse multipole (E 0+), expected in this region, allowed us to access the generalized form factor G 1 within the light-cone sum rule (LCSR) framework as well as the axial form factor G A. The data analyzed in this work were collected by the nearly 4π CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754-GeV electron beam on a proton target. The differential cross section and the π-N multipole E 0+/G D were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost Q 2 independent.
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Publication Date:
Report Number(s):
JLAB-PHY-12-1412; DOE/OR/23177-1959; arXiv:1201.0903
Journal ID: ISSN 0556-2813; PRVCAN; TRN: US1202538
Grant/Contract Number:
AC05-06OR23177
Type:
Accepted Manuscript
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 85; Journal Issue: 3; Related Information: JLAB Experiment Number: E99-107; Journal ID: ISSN 0556-2813
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; DIFFERENTIAL CROSS SECTIONS; ELECTRON BEAMS; FORM FACTORS; LIGHT CONE; MOMENTUM TRANSFER; MULTIPOLES; PRODUCTION; PROTONS; SPECTROMETERS; SUM RULES
OSTI Identifier:
1040720