Measurement of the single-spin asymmetry Ay0 in quasi-elastic 3He"3222378 (e,e'n) scattering at 0.4 < Q2 < 1.0 GeV/c2

Due to the lack of free neutron targets, studies of the structure of the neutron are typically made by scattering electrons from either H or He targets. In order to extract useful neutron information from a He target, one must understand how the neutron in a He system differs from a free neutron by taking into account nuclear effects such as final state interactions and meson exchange currents. The target single spin asymmetry Ay is an ideal probe of such effects, Corresponding author Email address: elena.long@unh.edu (E. Long) Deceased 9 May 2011. Preprint submitted to Physics Letters B May 14, 2019 as any deviation from zero indicates effects beyond plane wave impulse approximation. New measurements of the target single spin asymmetry Ay at Q 2 of 0.46 and 0.96 (GeV/c) were made at Jefferson Lab using the quasi-elastic 3He(e, en) reaction. Our measured asymmetry decreases rapidly, from > 20% at Q = 0.46 (GeV/c) to nearly zero at Q = 0.96 (GeV/c), demonstrating the fall-off of the reaction mechanism effects as Q increases. We also observed a small ǫ-dependent increase in Ay compared to previous measurements, particularly at moderate Q . This indicates that upcoming high Q measurements from the Jefferson Lab 12 GeV program can cleanly probe neutron structure from polarized He using plane wave impulse approximation.