New prediction of elastic scattering cross sections ratio R<sub>e<sup>+</sup> </sub> <sub>e<sup>−</sup> </sub> based on phenomenological two-photon exchange corrections
I. A. Qattan
Abstract
Abstract The proton’s electric and magnetic form factors (FFs) and their ratio R p = <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">G</mml:mi> <mml:mi>E</mml:mi> <mml:mi>p</mml:mi> </mml:msubsup> <mml:mo>/</mml:mo> <mml:msubsup> <mml:mi mathvariant="normal">G</mml:mi> <mml:mi>M</mml:mi> <mml:mi>p</mml:mi> </mml:msubsup> </mml:mrow> </mml:math> are fundamental and essential ingredients needed to parametrize the internal structure of the proton as well as many composite particles. However, the inconsistency in the results reported on these FFs and their ratio as measured by the Rosenbluth method and the polarization transfer method has led the community to believe that such a discrepancy is due to a systematic difference between the two methods. It was proposed that missing higher order radiative correction to the electron-proton elastic scattering cross section σ R ( ϵ, Q 2 ) and in particular two-photon exchange correction (TPE) should be applied in order to reconcile these measurements. The effect of TPE on electron-proton scattering observables was studied extensively in the last few years. However, the most direct method for measuring TPE contributions is the comparison of positron-proton and electron-proton elastic scattering cross sections ratio R e+ e− ( ϵ, Q 2 ). In this proceedings, I present a new prediction of the ratio R e+ e− as determined using a new parametrization of TPE corrections to σ R . I then compare my results to several previous phenomenological extractions, TPE hadronic calculations, and previous and recent direct measurements of R e+ e− .