Polarimeter for Jefferson Lab High Momentum Transfer Proton Form Factor Measurement (GEp-V)

The Jefferson Lab Hall A Super Bigbite Spectrometer (SBS) experimental program will allow for precision measurements of the nucleon electromagnetic form factors. In particular, SBS experiment E12-07-109 (GEp) will measure the proton electromagnetic form factor ratio G_E^P/G_M^P, extending the range of data to high Q² with high precision. GEp will use the recoil polarization technique in which a longitudinally polarized electron beam is scattered off a fixed unpolarized proton target. The resulting transfer of polarization to the recoiling proton is measured and the ratio of the longitudinal and perpendicular components is directly proportional to the form factor ratio. The SBS spectrometer detector will measure this polarization ratio. Crucial to this measurement is the recoil polarimeter, largely made up of Gas Electron Multiplication (GEM) tracking detectors which measure particle trajectories to high precision. These detectors have been designed, built, and tested, and are currently being prepared for the GEp-V experiment. An overview of this polarimeter and the work that has gone into it will be presented.