The He-4(e, e ' p) cross section at high missing energies

The He-4(e, e' p) reaction has been studied in a kinematic regime in which short-range correlations are expected to have a strong impact on the reaction strength. The measured cross sections exhibit a bump-shaped structure at missing energies corresponding to quasi-free knockout of two nucleons. The results of microscopic calculations, that account for meson-exchange currents, intermediate Delta -excitation and final-state interactions, reproduce the data satisfactorily. The calculations indicate that at small proton emission angles the cross section is dominated by knockout of a correlated nucleon pair.

Proton detection with large-acceptance scintillator detection systems in electron-scattering environments

Two highly segmented plastic-scintillator arrays have been developed for proton detection in electron scattering experiments. The detectors subtend solid angles of 225 and 550 msr and cover energy ranges of 50-225 and 25-165 MeV, respectively. The charge and arrival time of each photomultiplier signal are digitized by flash ADCs and temporarily stored in a dual-port memory. The readout parameters are computer controlled, tuned, and monitored. These detectors have been employed in (e, e'p) and (e, e'pp) experiments for proton emission angles greater than 30 degrees and for luminosities up to 10(36) nucleons cm(-2) s(-1). The singles counting rates in the scintillator elements of the first layers were about 0.5 x 10(6) particles s(-1) and the trigger rate 1 MHz. The measured resolution in the excitation energy and timing spectra are 2.7% and 0.7 ns, respectively. (C) 1999 Elsevier Science B.V. All rights reserved

Deuteron electrodisintegration at high missing momenta

The reaction (2)H(e, e'p) has been studied at an invariant mass W of 1050 MeV, i.e. well below the Delta(1232) resonance, Cross sections have been obtained at values of Q(2), the four-momentum transfer squared, of 0.10, 0.20, and 0.28 (GeV/c)(2), covering a missing-momentum range from 150 to 700 MeV/c. The data are compared to the results of covariant calculations of Tjon, and the results of calculations based on a Schrodinger formalism due to Laget and the Mainz group, respectively. The data are well described by the calculations of the Mainz group, whereas they are underestimated by Tjon's calculations at high missing momenta. The calculations of Laget, on the other hand, overestimate the data at low missing momenta, but give a good account of the data at high missing momenta. More detailed considerations reveal that the Delta(1232) contributions are dominant at high missing momenta. However, the lacking Delta(1232) contribution in Tjon's calculations is not enough to explain the large discrepancy between his calculation and the present (2)H(e, e'p) data at high missing momentum. Probably the deuteron wave function employed in the covariant calculations has a D-state contribution that is too small

Deuteron electrodisintegration at high missing momenta

The reaction (2)H(e, e'p) has been studied at an invariant mass W of 1050 MeV, i.e. well below the Delta(1232) resonance, Cross sections have been obtained at values of Q(2), the four-momentum transfer squared, of 0.10, 0.20, and 0.28 (GeV/c)(2), covering a missing-momentum range from 150 to 700 MeV/c. The data are compared to the results of covariant calculations of Tjon, and the results of calculations based on a Schrodinger formalism due to Laget and the Mainz group, respectively. The data are well described by the calculations of the Mainz group, whereas they are underestimated by Tjon's calculations at high missing momenta. The calculations of Laget, on the other hand, overestimate the data at low missing momenta, but give a good account of the data at high missing momenta. More detailed considerations reveal that the Delta(1232) contributions are dominant at high missing momenta. However, the lacking Delta(1232) contribution in Tjon's calculations is not enough to explain the large discrepancy between his calculation and the present (2)H(e, e'p) data at high missing momentum. Probably the deuteron wave function employed in the covariant calculations has a D-state contribution that is too small.</p

The He-4(e,e ' p) cross section at large missing energy

The (e,e'p) reaction on He-4 nuclei was studied in kinematics designed to emphasize effects of nuclear short-range correlations. The measured cross sections display a peak in the kinematical regions where two-nucleon processes are expected to dominate. Theoretical models incorporating short-range correlation effects agree reasonably with the data

Proton detection with large-acceptance scintillator detection systems in electron-scattering environments

Two highly segmented plastic-scintillator arrays have been developed for proton detection in electron scattering experiments. The detectors subtend solid angles of 225 and 550 msr and cover energy ranges of 50-225 and 25-165 MeV, respectively. The charge and arrival time of each photomultiplier signal are digitized by flash ADCs and temporarily stored in a dual-port memory. The readout parameters are computer controlled, tuned, and monitored. These detectors have been employed in (e, e'p) and (e, e'pp) experiments for proton emission angles greater than 30 degrees and for luminosities up to 10(36) nucleons cm(-2) s(-1). The singles counting rates in the scintillator elements of the first layers were about 0.5 x 10(6) particles s(-1) and the trigger rate 1 MHz. The measured resolution in the excitation energy and timing spectra are 2.7% and 0.7 ns, respectively. (C) 1999 Elsevier Science B.V. All rights reserved