Measurement of the single-spin asymmetry Ay0 in quasi-elastic 3He↑(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 2H or 3He targets. In order to extract useful neutron information from a 3He target, one must understand how the neutron in a 3He 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 A y 0 is an ideal probe of such effects, as any deviation from zero indicates effects beyond plane wave impulse approximation. New measurements of the target single spin asymmetry A y 0 at Q 2 of 0.46 and 0.96 (GeV/ c ) 2 were made at Jefferson Lab using the quasi-elastic He ↑ 3 ( e , e ′ n ) reaction. Our measured asymmetry decreases rapidly, from &gt; 20 % at Q 2 = 0.46 (GeV/ c ) 2 to nearly zero at Q 2 = 0.96 (GeV / c ) 2 , demonstrating the fall-off of the reaction mechanism effects as Q 2 increases. We also observed a small ϵ-dependent increase in A y 0 compared to previous measurements, particularly at moderate Q 2 . This indicates that upcoming high Q 2 measurements from the Jefferson Lab 12 GeV program can cleanly probe neutron structure from polarized 3He using plane wave impulse approximation.