M. Bernheim

DEEP-INELASTIC ELECTRON SCATTERING FROM CARBON

Abstract We have measured the deep-inelastic electron scattering from carbon up to and including the Δ-region at 36°, 60°, 90° and 145°. The systematic decomposition of the transverse and longitudinal response functions has been obtained by means of a Rosenbluth-type analysis of the data in the momentum transfer interval 200 MeV/c /s |q| /s 600 MeV/c. A comparison with theoretical calculations which extend over the quasielastic and Δ-peak regions is presented. A reduction of the differences between our data and theory seems obtainable through the introduction of meson-exchange currents, resonant and non-resonant meson production, and the use of the shell model. Our experimental Coulomb sum-rule estimates at higher | q | agree with independent particle model predictions. We compare our results in the vicinity of the Δ-peak with the total absorption cross section for real photons.

Transverse and longitudinal response functions in deep inelastic electron scattering from 3He

Abstract We have measured inclusive electron scattering cross sections on 3 He at incident energies up to 667 MeV. The transverse and longitudinal response functions were extracted at four-momentum transfers between −0.1 (GeV/ c ) 2 and −0.3 (GeV/ c ) 2 and up to an energy transfer of 450 MeV. The data are compared to recent theoretical calculations which include many-body effects.

Momentum distribution of nucleons in the deuteron from the d(e, e′p)n reaction

Abstract The nucleon momentum distribution in the deuteron has been determined up to 340 MeV/ c by measuring the d(e, e′p)n reaction at an incident electron energy of 500 MeV. The data are well described even above p = 200 MeV / c by the most recent deuteron wave functions, in contrast with previous (e, e′p) and (p, 2p) results.

Longitudinal and transverse responses in quasi-elastic electron scattering from 208Pb and 4He

Abstract Longitudinal and transverse response functions, R L and R T , have been obtained in inclusive quasi-elastic electron scattering from 4 He and 208 Pb, for momentum transfers between 300 and 650 MeV/ c and energy transfers up to 350 MeV. A quenching of R L , ∼ 14% in 4 He and ∼ 50% in 208 Pb has been observed. Interpretations in terms of correlations and modification of nucleon form factors in the nuclear medium are discussed.

Exclusive deuteron electrodisintegration at high neutron recoil momentum

Abstract We have determined the 2 H(e, e′p)n cross section for neutron recoil momenta between 295 and 500 MeV/ c . In this region the 3 D 1 state contribution is predominant in the deuteron wave function. The high excitation energy ( E cm np = 179 MeV) and the small momentum transferred (|; q cm |; 2 = 1.66 fm − ) emphasize the influence of isobar configurations (IC). Experimental data are compared with calculations including isobar contributions, mesonic exchange currents and final state interactions.

The quasi-free 3He(e, e′p) reaction

The proton spectral function has experimentally been determined with the 3He(e, e′p) reaction for missing energies, 0<Em<70MeV, and recoil momenta, 0<PB<310 MeV/c. Experimental results are obtained for both the two-body, 3He(e, e′p)2H, and three-body breakup processes. Proton momentum density distributions, obtained in a PWIA analysis, are compared with theoretical calculations: Faddeev solutions with the RSC and Paris potentials, and variational calculations with various potentials, including those with a three-nucleon interaction term. Energy-weighted sum rule results are presented and compared with theoretical predictions. The coincidence cross sections are also compared with calculations which include the effects of final state interactions and meson exchange currents. Consistency of the results with PWIA is investigated in the framework of the Chew-Low extrapolation procedure.

A study of the electrodisintegration reaction 4He(e, e′ p)3H with transverse longitudinal separation

Abstract Longitudinal and transverse cross sections for the reaction 4 He(e, e′ p) 3 H were determined for missing momenta p m up to 190 MeV/ c and momentum transfers q up to 829 MeV/ c (at p m =90 MeV/ c ). “Experimental” spectral functions were obtained; the transverse one exhibits the free nucleon q -dependence at fixed p m and agrees with microscopic theories; the longitudinal spectral function is low by 30%.

Deep inelastic electron scattering from 12C

Deep-inelastic electron scattering from 12C was measured at 60°, 90°, 130° and 145° until 560 MeV incident electron energy. Longitudinal-transverse separation was achieved for ¦q2μ¦ < 6 fm−2 and energy-loss ω < 360 MeV. The longitudinal sum rule exhibits 80 % of the strength predicted by single particle model. The measured cross section between the quasi-elastic peak and the free Δ peak is compared to different theoretical models. Mesonic exchange current in proton-neutron pairs seems to play an important role.

A waterfall target for electron scattering experiments

A windowless waterfall target for electron scattering experiments on 16O is described. The thickness of the laminar film, adjustable between ∼ 45 mg/cm2 and ∼ 140 mg/cm2, has been proven to be particularly stable in time (within ± 0.5%) and insensitive to beam current up at least 20 μA. The whole target system remotely monitored on-line.

Two-body correlations in the 6Li nucleus through the (e, e′ d) reaction

Abstract The dependence on the momentum transfer q for the 6Li (e, e′ d) cross section has been measured. In the 6Li(e, e′ d)4Heg.s. channel, data can be reproduced assuming the reaction as a quasi-elastic deuteron knock-out process, where the 6Li valence nucleons are probed. When the residuum is in the continuum channel, this assumption does not match the data, unless a wave function different from that of a free deuteron is considered for the pair involved in the reaction.