Authors
Christy, M.; Gautam, T. ; Ou, L.; Schmookler, B.; Wang, Y.; Adikaram, D.; Ahmed, Zafir; Albataineh, H; Ali, S.; Aljawrneh, B.; Arrington, J. ; Reimer, P.
Abstract
We present new precision measurements of the elastic electron-proton scattering cross section for momentumtransfer (Q2) up to 15.75 (GeV/c)2. Combined with existing data, these provide an improved extraction of theproton magnetic form factor at high Q2and double the range over which a longitudinal/transverse separation ofthe cross section can be performed. The difference between our results and polarization data agrees with thatobserved at lower Q2and attributed to hard two-photon exchange (TPE) effects, extending to 8 (GeV/c)2therange of Q2for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify thesize of TPE contributions needed to explain the cross section at high Q2.