Measurement of the magnetic form factor of the neutron

The ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(e,e’n${)}^1$H quasielastic cross section was measured at ${\mathit{Q}}^2$ values of 0.109, 0.176, and 0.255 (GeV/c${)}^2$. The neutron detection efficiency was determined by the associated particle technique with the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(γ,pn) reaction for each of the three neutron kinetic energies. These ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(e,e’n) measurements of the coincidence cross sections are the first at low ${\mathit{Q}}^2$. The cross sections are sensitive primarily to the neutron magnetic form factor ${\mathit{G}}_{\mathit{M}}^{\mathit{n}}$ at these kinematics. The extracted ${\mathit{G}}_{\mathit{M}}^{\mathit{n}}$ values have smaller uncertainties than previous data and are consistent with the dipole parametrization at the two higher momentum transfers; at the lowest momentum transfer, the value of ${\mathit{G}}_{\mathit{M}}^{\mathit{n}}$ is ∼10% higher than the dipole value.