Speaker
Description
Measurements of the elastic electromagnetic form factors of the proton and neutron have been a central component of Jefferson Lab’s scientific program for almost four decades and have been important, among other things, in constraining Generalized Parton Distributions and testing the validity of the onset of perturbative quantum chromodynamics. The ratio of $G_E^p/G_M^p$ measured in the late 1990s at Jefferson Lab via the polarization transfer technique and published in 2000 showed that $G_E^p$ falls off more rapidly than $G_M^p$ at $Q^2>1$ GeV$^2$ in contradiction of results from cross section measurements using the Rosenbluth separation method. This led to the measurement of $G_E^p/G_M^p$ by the recoil poalrization method up to 8.5~GeV$^2$ in 2008. A new measurement of $G_E^p$ is under preparation with plans to reach as high as 12 GeV$^2$. With the form factor dropping as $Q^{-4}$ and the cross section as $Q^{-12}$, going to high $Q^2$ is a challenge, with a large acceptance needed for statistics and the ability to discriminate elastic events from the backgrounds at very high background rates. I will discuss the motivation for this new measurement and how some of the challenges will be met.
