We report the first measurement of the neutron electric form factor $G_E^n$ via $\vec{d}(\vec{e},e'n)p$ using a solid polarized target. $G_E^n$ was determined from the beam-target asymmetry in the scattering of longitudinally polarized electrons from polarized deuterated ammonia, $^{15}$ND$_3$. The measurement was performed in Hall C at Thomas Jefferson National Accelerator Facility (TJNAF) in quasi free kinematics with the target polarization perpendicular to the momentum transfer. The electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle segmented detector. We find $G_E^n = 0.04632\pm0.00616 (stat.) \pm0.00341 (syst.)$ at $Q^2 = 0.495$ (GeV/c)$^2$.
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The ratio of neutron and proton yields at quasifree kinematics was measured for the reactions 2H(e,e′n) and 2H(e,e′p) at momentum transfers Q2=0.125, 0.255, 0.417, and 0.605(GeV/c)2, detecting the neutron and the proton simultaneously in the same scintillator array. The neutron detection efficiency was measured in situ with the 1H(γ,π+)n reaction. From this the ratio R of 2H(e,e′n) and 2H(e,e′p) cross sections was determined and used to extract the neutron magnetic form factor GMn in a model insensitive approach, resulting in an inaccuracy between 2.1% and 3.3% in GMn.
Formfactor in nuclear magnetons.
The H2(e,e’n)1H quasielastic cross section was measured at Q2 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 H2(γ,pn) reaction for each of the three neutron kinetic energies. These H2(e,e’n) measurements of the coincidence cross sections are the first at low Q2. The cross sections are sensitive primarily to the neutron magnetic form factor GMn at these kinematics. The extracted GMn 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 GMn is ∼10% higher than the dipole value.
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We measured the elastic and inelastic scattering of electrons on deuterium at 180° for four incident energies (70, 140, 210 and 280 MeV). The data were analysed with a technique allowing an accurate comparison between experiment and theory. We observed a good agreement for the inelastic data with the expected cross section, using the presently available models and nucleon form factors. The experimental elastic cross section is systematically larger than the predicted cross sections.
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We have measured the absolute cross sections of the electron-deuteron scattering at q2=3.5 F−2 and obtained the complete inelastic spectrum. Three points for each spectrum are given with a 4% accuracy. The scattering angles, 60° and 130°, were chosen to allow the separation between electric and magnetic scattering. Calculations of radiative corrections were made in order to permit the comparison of the spectra with the inelastic-scattering theories.
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