New extraction of the e± elastic scattering cross-section ratio based on phenomenological two-photon exchange corrections

Abstract

The proton's electric GEp(Q2) and magnetic GMp(Q2) form factors (FFs) are fundamental quantities in nuclear and elementary particle physics. However, the inconsistency in the results on these FFs and their ratio μpRp=μpGEp/GMp as measured using the conventional Rosenbluth separation method, and the polarization transfer (PT) method suggested a systematic difference between the two techniques. To reconcile these measurements, several studies suggested that missing higher order radiative correction to the electron-proton elastic scattering cross section σR(e, Q2), and in particular two-photon exchange (TPE) corrections should be applied. While several analyses were performed to extract the TPE contributions, the most direct technique for measuring TPE is the comparison of electron-proton and positron-proton elastic scattering. In this study, I present a new extraction of the e± elastic scattering cross-section ratio Re+e− as determined using a new parametrization of the TPE corrections. I then compare my results to several previous phenomenological extractions, TPE hadronic calculations, and existing world data on the ratio Re+e− emphasizing mainly the recent high-Q2 measurements from the CLAS, VEPP-3 Novosibirsk, and OLYMPUS collaborations.