Measurements of the Electric Form Factor of the Neutron up to $Q^2=3.4{\mathrm{GeV}}^2$ Using the Reaction ${\mathrm{}}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\prime }n)pp$

The electric form factor of the neutron was determined from studies of the reaction ${\mathrm{}}^3\overrightarrow{\mathrm{He}}(\overrightarrow{e},e^{\prime }n)pp$ in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the $Q^2$ range over which it is known, we find $G_E^n=0.0236\pm 0.0017(\mathrm{stat})\pm 0.0026(\mathrm{syst})$, $0.0208\pm 0.0024\pm 0.0019$, and $0.0147\pm 0.0020\pm 0.0014$ for $Q^2=1.72$, 2.48, and $3.41{\mathrm{GeV}}^2$, respectively.

Figure 1

The ratio of ${\mu }_n{G}_E^n/G_M^n$ vs the momentum transfer with results of this experiment (solid triangles) and selected published data: diamonds [5], open triangles [6], circles [7], squares [8], open circles [12], and calculations: pQCD [28], RCQM [29], DSE [30], GPD [31], and VMD [32]. The curves labeled pQCD present pQCD-based scaling prediction [28] normalized to 0.3 at $Q^2=1.5{\mathrm{GeV}}^2$. The error bars for our data points show the statistical and the systematic uncertainties added in quadrature. Our fit is also shown; see parameterization in the text.

Figure 2

Nucleon flavor FF ratio $F_1^d/F_1^u$ vs $Q^2$. The band indicates the lattice QCD result [35]. The data and curves correspond to those shown in Fig. 1. See the text for details.