Studies of spin observables in [formula omitted] and [formula omitted] reactions at intermediate energies

Abstract

Recent measurements at 200 MeV of ( p , p′) spin transfer observables for excitation of discrete states show significant deviations from theoretical predictions based on the free NN t-matrix. Because the nuclear structure and distortions for these transitions are believed to be constrained by other data, this suggests that modifications of the in-medium NN interaction are needed, beyond Pauli blocking, to describe these processes. As a first step towards identifying the physical mechanisms that underlie these modifications, several phenomenological approaches have been tried to improved agreement between experiment and theory. The successes and limitations of these approaches will be discussed. Preliminary results from a detailed study of the ( p , p′γ) reaction for the 1 +, T=1 state in 12C at 15.11 MeV will also be presented.