Two Photon Exchange in Quasi-elastic and Deep-inelastic Scattering.

In this paper, I present an overview and preliminary results from three experiments at Jefferson Lab that were recently completed using a ³He gas target with polarization oriented normal to the scattering plane of unpolarized incident electrons. A target single spin asymmetry was formed by periodically flipping the direction of the target spin. In the reaction ↑³He(e,e[acute_underaccent]), the Born contribution is expected to be zero, giving direct sensitivity to two photon exchange. This asymmetry was measured in the quasi-elastic and deep-inelastic regimes with 0.1 < Q² < 1.0 GeV². The asymmetry is predicted to decrease by two-orders of magnitude for deep-inelastic versus quasi-elastic scattering. Preliminary results from these experiments will be presented. [ABSTRACT FROM AUTHOR]