Neutron Elastic Form Factor Ratio from Recoil Polarization

The GEn-RP experiment is among various form factor experiments with the Super-Bigbite Spectrometer (SBS) setup at Hall-A, Jefferson Lab and measures the ratio of electric to magnetic elastic form factors of the neutron, using recoil polarimetry techniques at in quasi-elastic electron-neutron scattering from a deuterium target. The ratio of these form factors is measured from the ratio of the transverse and the longitudinal components of the spin polarization, that is transferred to the recoiling neutron from the incident, longitudinally polarized electron beam. Both high-momentum, small-angle neutrons produced during elastic scattering and high-momentum small-angle protons produced by (charge exchange) are used to analyze the neutron polarization components after precessing through known magnetic fields. In addition, low momentum, large-angle protons produced during elastic scattering in active analyzer are detected, as a proof-of-principle measurement of the analyzing power.

This experiment will yield at kinematic point the three times higher yet published with recoil polarization and the experimental figure-of-merit information on the polarimetry along with the analyzing power will be used to optimize the future measurements of to reach higher values using recoil polarimetry techniques.