Quasielastic neutrino scattering: A measurement of the weak nucleon axial-vector form factor

The quasielastic reaction ν/sub μ/n→μ-p was studied in an experiment using the BNL 7-foot deuterium bubble chamber exposed to the wide-band neutrino beam with an average energy of 1.6 GeV. A total of 1138 quasielastic events in the momentum-transfer range Q2 = 0.06 --3.00 (GeV/c)2 were selected by kinematic fitting and particle identification and were used to extract the axial-vector form factor F/sub A/(Q2) from the Q2 distribution. In the framework of the conventional V-A theory, we find that the dipole parametrization is favored over the monopole. The value of the axial-vector mass M/sub A/ in the dipole parametrization is 1.07 +- 0.06 GeV, which is in good agreement with both recent neutrino and electroproduction experiments. In addition, the standard assumptions of conserved vector current and no second-class currents are checked