Y. Okuhara

Nuclear spin response to inelastic proton scattering: Finite geometry and absorption effects

Abstract Recent experiments have clearly demonstrated the ability of inelastic proton scattering to act as a precise probe of the nuclear spin response. Previous calculations based on infinite or semi-infinite matter models differ markedly from experiment in their prediction of longitudinal to transverse response function ratios. The present work indicates that finite geometry and absorption effects are crucial in bringing predictions closer to experiment. The effect of including isobar excitations is also investigated and assessed critically.

The missing charge problem and many-body correlation effects

Abstract The longitudinal sum rule, computed from recent electron scattering experiments is lower than theoretical predictions by about a factor of two. Although the effect of two-particle-two-hole correlations has generally been viewed as the predominant mechanism causing the quenching, its calculation is complex in medium weight and even prohibitive in heavy systems. We present here a simple and efficient method to estimate the effect of the many-particle-many-hole correlation, which borrows from Feshbachs reaction theory, and incorporates effects beyond the usual 2p-2h correlations. The method is introduced in the context of a fully microscopic RPA model and compared with experiment in the case of 40 Ca with particularly encouraging results.

Many particle-many hole nuclear correlations and the missing charge problem

Abstract The nuclear longitudinal sum rule, determined from recent electron scattering experiments is lower than theoretical predictions by about a factor of two. Although the effect of two particle-two hole correlations has generally been viewed as the predominant mechanism causing the quenching, its calculation is complex for medium and heavy nuclei. We present here a simple and efficient method to estimate the effect of the many particle-many hole correlation which borrows from Feshbachs reaction theory and incorporates effects beyond the usual 2p-2h correlations. The results are particularly encouraging in comparison with the data in 40 Ca, 48 Ca, and 56 Fe. The calculated sum rule also coincides with experiment at large momentum transfer in all cases studied.

Spin Excitations in a Schematic Model

Several recent results of proton inelastic scattering, some of them presented at this conference, have shed a new light on the character of the nuclear spin response 1,2. In particular, in a recent experiment using the proton beam at LAMPF, Glashauser et al. 3 have shown that spin-flip states in 40 Ca are strongly excited at excitation energies above 10 MeV and that nuclear spin excitations appear relatively suppressed at low excitation energies but surprisingly enhanced at higher excitation.