Off-shell effects in quasielastic electron nucleus scattering

Using the Ward-Takahashi identity, on-shell condition, bound Dirac equation and off-shell expansion, a reduced version of half off-shell virtual photon nucleon vertex has been suggested. The vertex are decomposed into several different order terms: the on-shell terms, first and second off-shell terms. The off-shell behaviour of the form factors is discussed in the one meson loop model. Using the reduced vertex and parametrized off-shell form factors the quasielastic response functions are calculated for several nuclei at ¦q¦–k_f and for⁵⁶Fe at large ¦q¦ up to 1.14 GeV/c and at ?q²=0.9 (GeV/c)². The Coulomb sums are evaluated and a comparison of the theoretical prediction with data is given. The off-shell electron nucleon cross section is calculated and compared with the “cc1” off-shell extrapolation.     

Scaling violation in quasielastic electron scattering

The scaling law in quasielastic electron scattering is broken due to exchange forces. The violation in the longitudinal response function is attributed to the central part of exchange forces, while in the transverse response the tensor part also leads to the breaking. The effects of one-boson exchange potentials are discussed.     

Spin-momentum correlations in quasielastic electron scattering from deuterium

The spin-momentum correlation parameter A(V)(ed) was measured for the 2H-->(e-->,e'p)n reaction for missing momenta up to 350 MeV/c at Q2 = 0.21 (GeV/c)(2) for quasielastic scattering of polarized electrons from vector-polarized deuterium. The data give detailed information about the deuteron spin structure and are in good agreement with the results of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment reveals in a most direct manner the effects of the D state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction.     

On the analysis for scaling in quasielastic electron scattering off nuclei

We consider problems related to the analysis for scaling in quasielastic electron scattering off nuclei, with particular consideration given to analysis of recent SLAC data. The need for full consistency in kinematics and covariance of the cross section is emphasized and errors in previous analyses are pointed out. On the theoretical side, a universality (of sorts) is described for the impulse approximation “prediction” of the scaling function.     

Eikonal analysis of Coulomb distortion in quasi-elastic electron scattering

An eikonal expansion is used to provide systematic corrections to the eikonal approximation through order 1/k ², where k is the wave number. Electron wave functions are obtained for the Dirac equation with a Coulomb potential. They are used to investigate distorted-wave matrix elements for quasi-elastic electron scattering from a nucleus. A form of effective-momentum approximation is obtained using trajectory-dependent eikonal phases and focusing factors. Fixing the Coulomb distortion effects at the center of the nucleus, the often-used ema approximation is recovered. Comparisons of these approximations are made with full calculations using the electron eikonal wave functions. The ema results are found to agree well with the full calculations.     

Nuclear effects on lepton polarization in charged-current quasielastic neutrino scattering

We use a correlated local Fermi gas (LFG) model, which accounts also for long distance corrections of the RPA type and final-state interactions, to compute the polarization of the final lepton in charged-current quasielastic neutrino scattering. The present model has been successfully used in recent studies of inclusive neutrino nucleus processes and muon capture. We investigate the relevance of nuclear effects in the particular case of τ polarization in tau-neutrino induced reactions for several kinematics of relevance for neutrino oscillation experiments.     

Spin-orbit distortion of the emerging nucleon in quasi-free electron scattering

Spin-orbit distortion of the emerging nucleon in quasi-free electron scattering is considered in the frame of a program aiming at examining the approximations involved in the theoretical treatment. The imaginary part of the spin-orbit coupling in the optical-model potential felt by the knocked out nucleon appears here to have a significant role. Its consequences in the case of the reaction ¹²C(e, e′p)¹¹B are discussed.     

Relativistic Hartree response function for quasielastic electron scattering on 12C and 40Ca

Relativistic response functions for quasielastic electron scattering on ¹²C and ⁴⁰Ca are calculated self-consistently within the framework of the Hartree approximation in the σ - ω model. The longitudinal response functions overestimate experimental data, whereas the transverse ones underestimate. The relativistic mean field approximation cannot resolve the difficulty to reproduce the observed longitudinal and transverse response functions simultaneously.     

RPA response function for quasielastic electron scattering in the relativistic σ-ω model

In the Hartree approximation for the relativistic σ-ω model, the σ-meson dominates the longitudinal response function for quasielastic electron scattering, through the effective mass of the nucleon. In the random phase approximation, however, the effective mass effect is cancelled by the particle-hole correlation due to the σ-meson exchange, and the ω-meson also plays an important role in the response function.     

The influence of short-range correlations on nucleon emission in electron scattering by nuclei

The nucleon emission induced by high-energy electrons is analysed in three experimental situations: electron-proton coincedence and single detection of electron or proton. The coincidence and proton detection experiments are recommended as sensible tools for studying the nuclear correlations.     

Low-energy electron scattering and dispersive effects

The role and the importance of the dispersive effects in the electron scattering from light nuclei are analyzed in connection with the 〈r²〉 determination by low-energy experiments.