Measurement of the Electric Form Factor of the Neutron at $Q^2=0.5$ and $1.0{\mathrm{G}\mathrm{e}\mathrm{V}}^2/c^2$

The electric form factor of the neutron was determined from measurements of the $\overrightarrow{d}(\overrightarrow{e},e^{\prime }n)p$ reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (${}^{15}\mathrm{N}\mathrm{D}_3$) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find $G_E^n=0.0526\pm 0.0033(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.0026(\mathrm{s}\mathrm{y}\mathrm{s})$ and $0.0454\pm 0.0054\pm 0.0037$ at $Q^2=0.5$ and $1.0(\mathrm{G}\mathrm{e}\mathrm{V}/c{)}^2$, respectively.

Figure 1

Comparison of $Q^2=1.0$ MC and data electron-neutron event distributions from all materials in the target for four kinematic variables: invariant mass $W$, $Q^2$, angle between the neutron and $\overrightarrow{q}$ in lab frame ${\theta }_{nq}$, and angle between neutron-proton system and the momentum transfer in the center-of-momentum frame ${\theta }_{np}^{cm}$. The solid grey histograms correspond to the data, and the dotted black histograms correspond to the simulation. Only the shaded regions, dominated by events from ${}^2\mathrm{H}$ were used to determine $G_E^n$.

Figure 2

Comparison of this experiment with data from recent measurements. The data points are diamonds [12], hollow squares [10], triangle [4], hollow circle [7], solid square [6], and plus sign [11]. Solid circles: This Letter. See text for a description of the curves.