Measurements of Proton Electromagnetic Form Factors and Two-Photon Exchange in Elastic Electron-Proton Scattering

Two experimental techniques, Rosenbluth separation and recoil polarization transfer, used to extract the proton's electromagnetic form factors ratio, yield markedly different results. Modern theoretical calculations suggest that two-photon exchange is responsible for the observed discrepancy and that it is epsilon dependent.
Jefferson Lab Experiment E05-017 was designed to measure the two-photon exchange contribution over a wide range of kinematics. In contrast with the conventional Rosenbluth method, E05-017 detected the elastically scattered proton rather than the electron returning a much more precise extraction of the form factor ratios.
This thesis reports the preliminary results of the reduced cross sections extraction determined at 112 kinematic settings. The cross section measurements were used to calculate the ratio at sixteen values of the four-momentum transfer squared significantly improving the available precision of unpolarized measurements in the low-to-modest and in the very high four-momentum transfer squared range. In addition, new limits on the deviation from linearity in the Rosenbluth plot were determined at each setting, featuring highly detailed measurements with more than ten $\varepsilon$ points at $Q^{2}=\SI{0.98}{\GeV^{2}}$ and $\SI{2.29}{\GeV^{2}}$.