Speaker
Brian Raue
(Florida International University)
Description
Since the discovery of the discrepancy between Rosenbluth and polarization-transfer measurements of the proton form-factor ratio $G_E/G_M$ there has been a renewed interest in measuring contributions to the elastic cross section from two-photon exchange (TPE). Three recent experiments conducted at CLAS, VEPP-3, and OLYMPUS directly determined the real part of the TPE amplitude by measuring the ratio of elastic $e^+p$ and $e^-p$ cross sections at $Q^2$ up to about 2 GeV$^2$. I will discuss these results and present the results of an analysis that compared them to recent models of TPE that largely reconcile the two types of form-factor measurements. I will also discuss the possibility of extending the TPE measurements at Jefferson Lab to higher $Q^2$ where the form-factor discrepancy suggests a large TPE contribution.
Primary author
Brian Raue
(Florida International University)
