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Title: Measurement of the target-normal single-spin asymmetry in quasielastic scattering from the reaction He 3 ( e , e ' )

Journal Article · · Physical Review Letters

We report the first measurement of the target single-spin asymmetry, Ay, in quasi-elastic scattering from the inclusive reaction 3He↑ (e,e') on a 3He gas target polarized normal to the lepton scattering plane. Assuming time-reversal invariance, this asymmetry is strictly zero for one-photon exchange. A non-zero Ay can arise from the interference between the one- and two-photon exchange processes which is sensitive to the details of the sub-structure of the nucleon. An experiment recently completed at Jefferson Lab yielded asymmetries with high statistical precision at Q2= 0.13, 0.46 and 0.97 GeV2. These measurements demonstrate, for the first time, that the 3He asymmetry is clearly non-zero and negative with a statistical significance of (8-10)σ. Using measured proton-to-3He cross-section ratios and the effective polarization approximation, neutron asymmetries of -(1-3)% were obtained. The neutron asymmetry at high Q2 is related to moments of the Generalized Parton Distributions (GPDs). Our measured neutron asymmetry at Q2=0.97 GeV2 agrees well with a prediction based on two-photon exchange using a GPD model and in addition provides a new independent constraint on these distributions.

Research Organization:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Contributing Organization:
Jefferson Lab Hall A Collaboration
Grant/Contract Number:
AC05-06OR23177
OSTI ID:
1224078
Alternate ID(s):
OSTI ID: 1224147
Report Number(s):
JLAB-PHY-15-2021; DOE/OR/23177-3321; arXiv:1502.02636; PRLTAO; National Science Foundation of China and UK STFC grants 57071/1, 50727/1.; TRN: US1600790
Journal Information:
Physical Review Letters, Vol. 115, Issue 17; ISSN 0031-9007
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 22 works
Citation information provided by
Web of Science

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Cited By (6)

The spin structure of the nucleon journal June 2019
Lepton mass effects for beam-normal single-spin asymmetry in elastic muon-proton scattering journal November 2019
The spin structure of the nucleon journal January 2005
The spin structure of the nucleon journal January 1994
The Spin Structure of the Nucleon: Proceeding of International School of Nucleon Structure: 1st Course conference April 2017
Lepton mass effects for beam-normal single-spin asymmetry in elastic muon-proton scattering text January 2019

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