Measurement of the neutron electric form factor in the reaction at MAMI

Abstract

A measurement of the ratio GnE/GnM at a four momentum transfer Q2 = 1.5 (GeV/c)2 has been carried out at the Mainz Microtron in 2008 in order to extract the electric Sachs form factor of the neutron (GnE) with the magnetic form factor (GnM) as input. MAMI-C provided a 1.5 GeV polarized electron beam, a polarized 3He gas target served as an effective polarized neutron target to allow the study of the process The scattered electrons were detected with a magnetic spectrometer of the A1-collaboration. To detect the recoil neutrons in coincidence with the electrons, a nucleon detector was installed. It consisted of a plastic scintillator array inside a heavy lead shield. Exploiting beam helicity asymmetries for different target polarization orientations, GnE/GnM can be extracted.