Measurement of the neutron electric form factor GE,n in the quasifree 2H((e)over-right-arrow, e′(n)over-right-arrow)p reaction

The electric form factor of the neutron G(E.n) has been measured in the quasifree H-2((e) over right arrow, e'(n) over right arrow)p reaction using the 855 MeV polarized cw electron beam of the Mainz Microtron MAMI. The polarization of the scattered neutrons was analyzed in a polarimeter consisting of two walls of plastic scintillators. The precession of the neutron spin in a magnetic field was used for the first time to circumvent the measurement of the effective analyzing power of the polarimeter and the beam polarization. In this way G(E,n) could be determined with little model dependence and experimental uncertainties, The result G(E,n)(0.34 GeV2/c(2)) = 0.0611 +/- 0.0069(stat) ((+0.0069)(-0.0055))(syst) is larger than previously assumed.