Spin Observables in Coincidence Electron Scattering from Nuclei

Abstract

A theoretical description of nucleon knockout reactions initiated by polarized electron scattering from polarized nuclei is presented. Explicit expressions for the complete set of reduced response functions (independent of the polarization angle) that can be experimentally obtained assuming plane waves for the electron are given in a general multipole expansion. The formalism is applied to the particular case of closed-shell-minus-one nuclei using two models for the ejected nucleon, including the final-state interaction phenomenologically with a complex optical potential and in the factorized plane-wave impulse approximation. Relativistic effects in the kinematics and in the electromagnetic current are incorporated throughout -specifically a new expansion of the electromagnetic current in powers only of the struck nucleon momentum is employed. Results are presented for the nucleus 39 K.

Origin of relativistic effects in the reaction2H(e,e′p)nat GeV energies

“…This conjecture is based on the large enhancement of the transverse-longitudinal response observed in this scheme, which was also seen in the fully relativistic calculation of [3]. If this conjecture is indeed true, relativity could be taken into account by applying the operator introduced in [1,[4][5][6] together with non-relativistic wave functions to the calculation of electro-nuclear reactions. This would obviously be very useful.…”

Effects of short-range correlations in(e,e′p)reactions and nuclear overlap functions

“…[23,29]. The formalism can also be applied to the present case of J = 0 nuclei, where some simplification of the multipoles given in ref.…”

“…The following equations we write in this appendix have been obtained, after some work, from the corresponding equations of ref. [23] for the particular case J = 0 (J being in [23] the angular momentum corresponding to a multipole expansion in terms of spherical harmonics Y J M (θ * , φ * ) of the nuclear polarization angles).…”

“…We use the DWIA model of [23,24] which includes a new expansion of the relativistic electromagnetic current in powers of the missing momentum, but it is not expanded in q or ω. Combined with relativistic kinematics, this relativized model was shown in ref.…”

Final-state interaction and recoil polarization in reactions: comparison with the polarized target case

“…Analyses of the complete set of polarization observables in (e, e ′ p) only exist for the case of light nuclei, in particular deuterium [28]- [33,34], but not for mediumweight nuclei. In the present paper we apply the DWIA model of [11,12,35] to describe proton knockout from the d 3/2 shell of 40 Ca for various recoil polarization directions, and compare the results with those found for the model of [25,26,36] of proton knockout from the same shell of polarized 39 K.…”