GEn-Recoil Polarimetry Experiment in Jefferson Lab SBS Program

The Super BigBite Spectrometer (SBS) program at JLab aims to measure nucleon electromagnetic form factors (EMFFs) at high momentum transfers. The GEn-RP experiment will measure the neutron EMFF ratio GEn/GMn through recoil polarimetry at Q2 = 4.5 (GeV/c)². This involves the elastic scattering of electrons off neutrons in a liquid deuterium target. The BigBite (BB) spectrometer detects electrons, while SBS tracks and determines the neutron's polarization. Two polarimetry techniques are used: charge-exchange np → pn with a passive Fe analyzer, and conventional np → np scattering with an active CH analyzer. GEn-RP acts as the initial validation of the charge-exchange method, by directly comparing it to the conventional approach. This experiment will serve to optimize future high Q2 experiments that measure GEn/GMn. In the experiment, BB and SBS utilize gas electron multiplier detectors (GEMs) for particle tracking. A set of in-line GEM trackers and recoil-polarimeter GEM trackers will be used. Installation and testing of GEM tracking detectors are ongoing at JLab. Experiment readiness of the tracking detector layers will be presented.