Measurement of the target-normal single-spin asymmetry in quasielastic scattering from the reaction
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
Web of Science
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
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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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