Multipole decomposition of Gamow–Teller strength

Abstract

Doubly differential continuum cross sections from the 90Zr(p, n)90Nb reaction have been analyzed via a multipoledecomposition technique. No quasi-free charge-exchange background has been subtracted, following the assumption that the observed cross sections are primarily due to one-step charge-exchange leading to 1p–1h states of all multipolarities to all excitations. The theoretical shapes of the differential cross sections for each Jπ multipole have been taken from random-phase approximation (RPA)–distorted-wave impulse approximation (DWIA) calculations. The experimental dσ/dΩ, for each 1 MeV excitation-energy bin have been decomposed into different multipole components by a least squares fit. This RPA-based analysis should determine the Jπ = 1+ cross sections with different, and also fewer, assumptions than usual for describing the underlying background. It can be of general importance in determining the extent of possible quenching of Gamow–Teller (GT) strength. The present decomposition accounts for all the theoretically predicted GT strength. The purpose of the present report is to illustrate an analysis based on RPA–DWIA shapes rather than to present final-decomposition results.