Comparison of polarization and analyzing power for the 15N(p, n) 15O reaction

Abstract

The analyzing power A y ( θ) and polarization P y ( θ) for the 15N(p, n 0) 15O reaction have been measured for E p = 4.5–11.3 MeV. The values of the two observables are nearly the same above 11 MeV, where a “quasi-elastic” view of the (p, n) reaction to the analog state should be applicable. Below 10 MeV, however, large spin-flip amplitudes and isospin-mixing ratios provide the two major conditions needed to obtain P y ( θ) ≠ A y ( θ), and dramatic differences between the two observables are observed. The size of the differences and their dependence on energy are similar to the results predicted by shell-model calculations. The P y ( θ) and A y ( θ) measurements have been combined with existing cross-section data to provide information about spin-flip processes. We also comment on the connection between comparisons of P y ( θ) and A y ( θ) in charge-symmetric (p, n) reactions and the recent controversial measurements of a difference between the values of P y ( θ) for a reaction and A y ( θ) for the inverse reaction.