New results from BLAST on the nucleon electromagnetic form factors
Recently, a new experiment was carried out in the South Hall Ring at the MIT-Bates Accelerator Laboratory. This experiment utilized a polarized electron beam, a pure hydrogen (deuterium) internal polarized gas target, and the symmetric Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The proton electric to magnetic form factor ratio, GEpG Mp at Q2= 0.15 - 0.65 (GeV/c)2 has been determined from the experiment by measuring the spin-dependent ep elastic scattering asymmetry in both sectors simultaneously. This is the first experiment to measure GEpGMp using a polarized proton target, which is complementary to recoil polarimetry experiments. The neutron magnetic form factor GMn has been extracted from the measurement of the spin-dependent asymmetry from the inclusive d(e,e) process in a similar Q2 with a vector polarized deuterium target, and the neutron electric form factor GEn has been extracted by measuring the spin-dependent asymmetry from the coincidence d(e,e′n) process simultaneously. Preliminary results on the nucleon form factors from the BLAST experiment are presented. © 2006 American Institute of Physics.
