Precision Measurements of the Proton Elastic Form Factor Ratio

Abstract

New high precision polarization measurements of the proton elastic form factor ratio in the Q2 range from 0.3 to 0.7 [GeV/c]2 have been made. These elastic H(e, e’p) measurements were done in Jefferson Lab’s Hall A using 80% longitudinally polarized electrons and recoil polarimetry. For 1 [GeV/c]2, previous polarization data indicated a strong deviation of the form factor ratio from unity which sparked renewed theoretical and experimental interest in how two‐photon diagrams have been taken into account. The new high precision data indicate that the deviation from unity, while small, persists even at Q2 less than 1 [GeV/c]2.