Abdellah Ahmidouch

Measurements of Deuteron Photodisintegration up to 4.0 GeV

The first measurements of the differential cross section for the d(γ,p)n reaction up to 4.0 GeV were performed at the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson Laboratory. We report the cross sections at the proton center-of-mass angles of 36°, 52°, 69°, and 89°. These results are in reasonable agreement with previous measurements at lower energy. The 89° and 69° data show constituent-counting-rule behavior up to 4.0 GeV photon energy. The 52° and 36° data disagree with the counting-rule behavior. The quantum chromodynamics (QCD) model of nuclear reactions involving reduced amplitudes disagrees with the present data.

Hypernuclear spectroscopy using the (e, e'K+) reaction

A pioneering experiment in {lambda} hypernuclear spectroscopy, undertaken at the Thomas Jefferson National Accelerator Facility (J Lab), was recently reported. The experiment used the high precision, continuous electron beam at JLab, and a special arrangement of spectrometer magnets to measure the hypernuclear spectrum from C and {sup 7}Li targets using the (e,eK{sup +}) reaction. The {sub {lambda}}{sup 12}B spectrum found in this investigation was previously published, but is reported here in more detail, with improved resolution. In addition, the results of a {sub {lambda}}{sup 7}He spectrum also obtained in the experiment, are shown. This latter spectrum indicates the need for a more detailed few-body calculation of the hypernucleus and the reaction process. The success of the experiment demonstrates the potential of the (e,eK{sup +}) reaction for high resolution spectroscopy of hypernuclear spectra.

Proton G_E/G_M from beam-target asymmetry

The ratio of the protons electric to magnetic form factor, G{sub E}/G{sub M}, can be extracted in elastic electron-proton scattering by measuring cross sections, beam-target asymmetry, or recoil polarization. Separate determinations of G{sub E}/G{sub M} by cross sections and recoil polarization observables disagree for Q{sup 2}>1 (GeV/c){sup 2}. Measurement by a third technique might uncover an unknown systematic error in either of the previous measurements. The beam-target asymmetry has been measured for elastic electron-proton scattering at Q{sup 2} = 1.51 (GeV/c){sup 2} for target spin orientation aligned perpendicular to the beam momentum direction. This is the largest Q{sup 2} at which G{sub E}/G{sub M} has been determined by a beam-target asymmetry experiment. The result, {mu}G{sub E}/G{sub M}=0.884{+-}0.027{+-}0.029, is compared to previous world data.

Nuclear transparency from quasielastic A(e,e^{'}p) reactions up to Q^{2}=8.1 (GeV/c)^{2}

The quasielastic (e,e

NEUTRON ELECTRIC FORM FACTOR VIA RECOIL POLARIMETRY

^prime

Observation of the Helium 7 {Lambda} hypernucleus by the (e,e'K+) reaction

p) reaction was studied on targets of deuterium, carbon, and iron up to a value of momentum transfer

Excited baryon form factors at high Q2

Q^2

Measurements of the neutron electric to magnetic form factor ratio G{sub En}/G{sub Mn} via the {sup 2}H(e{yields},e{sup '}n{yields}){sup 1}H reaction to Q{sup 2}=1.45 (GeV/c){sup 2}

of 8.1 (GeV/c)

Measurement of the Electric Form Factor of the Neutron through {rvec d}({rvec e},e{prime}n)p

^2

Measurement of the Electric Form Factor of the Neutron through d-vector(e-vector, e'n)p

. A nuclear transparency was determined by comparing the data to calculations in the Plane-Wave Impulse Approximation. The dependence of the nuclear transparency on