Measurement of the target single-spin asymmetry in quasi-elastic region from the reaction ³He↑(e, e̷̷̷̷)

A measurement of the inclusive target single-spin asymmetry, A[subscript y] ³He, has been performed using the quasi-elastic ³He↑(e, e̷̷̷̷) reaction with a vertically polarized ³He target at Q̷̷̷̷² values of 0.13, 0.46 and 0.97 GeV̷̷̷². This asymmetry vanishes under the one photon exchange assumption. But the interference between two-photon exchange and one-photon exchange gives rise to an imaginary amplitude, so that a non-zero A[subscript y] is allowed. The experiment, conducted in Hall A of Jefferson Laboratory in 2009, used two independent spectrometers to simultaneously measure the target single-spin asymmetry, A[subscript y] ³He. Using the effective polarization approximation, the neutron single-spin asymmetries, $A[superscript n, subcript y], were extracted from the measured ³He asymmetries. The measurement is the first to firmly establish a non-vanishing A[subscript y]. Non-zero asymmetries were observed at all Q̷̷̷̷² points, and the final overall precision is an order of magnitude improved over the existing proton data. The data provide new constraints on Generalized Parton Distribution (GPD) models and new information on the dynamics of the two-photon exchange process.Ph. D.Includes bibliographical referencesby Yawei Zhan