Speaker
Description
Over the past three decades at Jefferson Lab, there have been multiple experiments aimed at understanding the internal structure of nucleons. This is often done by measuring the electromagnetic form factors (FF) of these nucleons, at an increasingly higher momentum transfer squared, $Q^2$. The last of these experiments is GEp-V, which aims to measure the ratio of the electromagnetic form factors of the proton, $G^{p}_{E}/G^{p}_{M}$, up to a central $Q^2$ around 11 GeV$^2$. Although there is existing data up to this $Q^2$, its uncertainty is large due to the use of the Rosenbluth separation method. Rosenbluth separation assumes one-photon exchange, but as $Q^2$ gets large, contributions from two-photon exchange are no longer negligible. An alternative approach is to use the recoil polarization method, where a polarized electron beam interacts with an unpolarized hydrogen target and a polarization transfer occurs. With this method, the effects of two-photon exchange are less severe and $G^{p}_{E}/G^{p}_{M}$ can be obtained directly from the polarization transfer ratio. Using the recoil polarization method, SBS plans to make a more accurate measurement of $G^{p}_{E}/G^{p}_{M}$.