Cross sections and analyzing powers for the ((p)over-right-arrow,n) reaction on 3He and 4He at 200 MeV

Double-differential cross sections and analyzing powers A, for the ((p) over right arrow,n) reactions on He-3 and He-4 were measured at 200 MeV between (0)lab= 0 degrees and 44 degrees. The neutron spectra from He-3((p) over right arrow,n) are dominated by the quasifree scattering peak and show no evidence for resonances in the three-proton system. The spectra from He-4((p) over right arrow,n) exhibit strong resonance behavior in the p(3)He system at low relative p3He energies owing to the excitation of known L=1 resonances in Li-4, but there is no distinct quasifree peak in the measured spectra. The experimental A, for He-3((p) over right arrow,n,n), averaged over the experimental range of neutron energies, are similar to those for free nucleon-nucleon (NN) scattering, whereas for He-4((p) over right arrow,n) the A(y) are generally larger than the free values, The cross sections at far forward angles for both He-3 and He-4 appear to be suppressed relative to the free NN cross sections by Pauli blocking. At most angles, the shapes of the cross section spectra from both He-3 and He-4 are reproduced by distorted-wave impulse approximation (DWIA) calculations using a quasifree scattering model. Specifically for He-4((p) over right arrow,n), the model requires the use of an optical potential which has a strong L=1 potential resonance corresponding to the low-lying L=1 states in Li-4.