High-Q² Measurement of Proton Electromagnetic Form Factor Ratio G_Ep/G_Mp using the Super BigBite Spectrometer

Previous measurements of the proton electromagnetic form factor ratio G_Ep/G_Mp using the polarization transfer method upended long-held notions regarding the proton's structure and exposed the limits of applicability of the widely-used one-photon-exchange approximation in the interpretation of electron-nucleus scattering experiments at high energies. Nucleon form factor measurements at large values of momentum transfer Q² continue to be of high interest for constraining the theoretical modeling of the nucleon in the challenging region of transition between non-perturbative and perturbative QCD, and for revealing the relevant degrees of freedom in explaining and predicting the nucleon's short-distance structure. The family of experiments in Jefferson Lab's (JLab's) experimental Hall A known as the Super BigBite Spectrometer (SBS) program was designed to study two-particle coincidence reactions in "hard" electron-nucleus scattering by combining moderately large solid angle acceptance with large momentum bite and high-luminosity capability at forward scattering angles. Among the major goals of the SBS program is to measure the electric and magnetic form factors of proton and neutron to Q² ≥ 10 GeV² with unprecedented precision. The SBS program started in 2021 with several experiments focused on neutron form factors, and is approximately 50% complete as of this writing. The planned measurements of the proton G_E/G_M ratio to Q² = 12 GeV² using the polarization transfer method, designated a "high impact experiment" by JLab's Program Advisory Committee, are currently scheduled to run in 2024. In this talk, I will give an overview of these measurements and the status of preparations for the upcoming experiment run.