Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction He3(e,e)X

J. Katich et al.
Phys. Rev. Lett. 113, 022502 – Published 11 July 2014
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Abstract

We report the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction He3(e,e)X on a polarized He3 gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero if two-photon-exchange contributions are included. The experiment, conducted at Jefferson Lab using a 5.89 GeV electron beam, covers a range of 1.7<W<2.9  GeV, 1.0<Q2<4.0  GeV2 and 0.16<x<0.65. Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to-He3 cross-section ratios. The measured neutron asymmetries are negative with an average value of (1.09±0.38)×102 for invariant mass W>2  GeV, which is nonzero at the 2.89σ level. Our measured asymmetry agrees both in sign and magnitude with a two-photon-exchange model prediction that uses input from the Sivers transverse momentum distribution obtained from semi-inclusive deep-inelastic scattering.

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  • Received 7 November 2013

DOI:https://doi.org/10.1103/PhysRevLett.113.022502

© 2014 American Physical Society

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Vol. 113, Iss. 2 — 11 July 2014

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