Status of the SBS GEP Experiment Run and a First Look at Data

The SBS (Super Bigbite Spectrometer) GEP experiment will measure the proton electric and magnetic form factor ratio (G^p_E / G^p_M) at four Q² points: 3.7, 5.7, 8.1, and 12.0 GeV², using the polarization transfer technique. The Super Bigbite apparatus at Hall A of JLab was originally designed and approved for the GEP experiment. However, several experiments to measure neutron elastic form factors have already been successfully completed using various configurations of the SBS detector packages. The GEP experiment will run with some modifications and additions to the SBS detector packages. Longitudinally polarized electrons will scatter from a liquid hydrogen target, transferring polarization to the recoiling protons. A moderate solid-angle spectrometer, consisting of a dipole magnet, a proton polarimeter, and a hadron calorimeter, will detect the recoiling protons. The ratio of the transverse and longitudinal polarization components of the proton will be extracted, which is directly proportional to the ratio G^p_E / G^p_M. The scattered electrons will be detected by a novel electron calorimeter (ECal) in coincidence with the proton to suppress the overwhelmingly large inelastic background contributions at these high-Q² settings. This talk will provide an overview and a status report on the ongoing GEP experiment.