J. L. Matthews

-Measurement of the proton's electric to magnetic form factor ratio from 1H(over -->)(e(over -->),e'p).

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.

Measurement of the proton's electric to magnetic form factor ratio from H→1(e→,e′p)

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.

The Charge Form Factor of the Neutron at Low Momentum Transfer from the H-2-polarized (e-polarized, e-prime n) p Reaction

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.

The Charge Form Factor of the Neutron at Low Momentum Transfer from the

We report new measurements of the neutron charge form factor at low momentum transfer using quasielastic electrodisintegration of the deuteron. Longitudinally polarized electrons at an energy of 850 MeV were scattered from an isotopically pure, highly polarized deuterium gas target. The scattered electrons and coincident neutrons were measured by the Bates Large Acceptance Spectrometer Toroid (BLAST) detector. The neutron form factor ratio GEn/GMn was extracted from the beam-target vector asymmetry AedV at four-momentum transfers Q2=0.14, 0.20, 0.29, and 0.42 (GeV/c)2.

^{2}\vec{\rm H}(\vec{\rm e},{\rm e}'{\rm n}){\rm p}

Abstract Measurements have been carried out of the distribution in energy and angle of the high-energy protons emitted in the photodisintegration of 6 Li, with some limited studies also of 7 Li and 12 C. The experiments were performed at the University of Saskatchewan Accelerator Laboratory using a 100 MeV bremsstrahlung beam. Protons of energies between 40 MeV and 95 MeV were detected with about 4% resolution, at eight angles from 45° to 126° by an array of plastic scintillation counter telescopes. Proton spectra for “monochromatic” photons were obtained by forming a properly normalized difference between spectra measured with 102 and 95 MeV bremsstrahlung beams. The 6 Li(γ, p) data are compared with the prediction of a phenomenological quasi-deuteron model, and this model is found to reproduce satisfactorily the shape and scale of the data over the entire range of the measurement. The experimental results are also discussed in terms of a single-particle model. A Born approximation calculation using shell-model wave functions does not provide sufficient amplitudes at high momenta to account for the 6 Li(γ, p) data.

Reaction

The neutron-proton bremsstrahlung process (np{yields}np{gamma}) is known to be sensitive to meson exchange currents in the nucleon-nucleon interaction. The triply differential cross section for this reaction has been measured for the first time at the Los Alamos Neutron Science Center, using an intense, pulsed beam of up to 700-MeV neutrons to bombard a liquid hydrogen target. Scattered neutrons were observed at six angles between 12 deg. and 32 deg., and the recoil protons were observed in coincidence at 12 deg., 20 deg., and 28 deg. on the opposite side of the beam. Measurement of the neutron and proton energies at known angles allows full kinematic reconstruction of each event. The data are compared with predictions of two theoretical calculations, based on relativistic soft-photon and nonrelativistic potential models.

Photoprotons from lithium and carbon with 100 MeV bremsstrahlung

Abstract The differential cross section for the reaction 16 O(γ,p 0 ) 15 N has been measured over the angular range 22°–144° at E γ =196 MeV. The data are found to be in disagreement with published theoretical calculations which include meson exchange and Δ (1232) amplitudes.

Differential cross section for neutron-proton bremsstrahlung

There have been very few measurements of the total cross section for np scattering below 500 keV. In order to differentiate among NN potential models, improved cross section data between 20 and 600 keV are required. We measured the np and nC total cross sections in this energy region by transmission; a collimated neutron beam was passed through CH2 and C samples and transmitted neutrons were detected by a BC-501A liquid scintillator. Cross sections were obtained with a precision of 1.1-2.0% between 150 and 800 keV using ratios of normalized neutron yields measured with and without the scattering samples in the beam. In energy regions where they overlap, the present results are consistent with existing precision measurements, and fill in a significant gap in the data between En = 150 and 500 keV.

The 16O(γ,p0)15N reaction at Eγ = 196 MeV

The MIT‐Bates Compton Polarimeter, a laser back‐scattering device, is used to measure the polarization of electron beams circulating in the South Hall Ring for a range of energies between 300 and 1000 MeV. The apparatus is described in detail and compared to other polarimeters operating within a similar energy region. Preliminary polarization results at 850 MeV are presented.

Measurements of the neutron-proton and neutron-carbon total cross section from 150 to 800 keV

Abstract A Compton polarimeter is being developed for the MIT/Bates South Hall Storage Ring. This polarimeter will be used to make measurements of the polarization of stored electron beams with energies below 1 GeV during internal target experiments.