Cross-sections and analyzing powers for $(p,n)$ reactions on ${}^{3}{\rm He}$ and ${}^{4}{\rm He}$ at 346 MeV

TL;DR

This study measures cross-sections and analyzing powers for $(p,n)$ reactions on ${}^{3}{ m He}$ and ${}^{4}{ m He}$ at 346 MeV, comparing experimental data with theoretical PWIA calculations to understand quasielastic and resonance contributions.

Contribution

First detailed measurements of $(p,n)$ reactions on ${}^{3}{ m He}$ and ${}^{4}{ m He}$ at this energy, with analysis of quasielastic and resonance effects using PWIA.

Findings

Quasielastic scattering dominates at large angles for both nuclei.

Resonance effects are prominent at small angles in ${}^{4}{ m He}$ spectra.

PWIA calculations reasonably reproduce large-angle spectra.

Abstract

The cross-sections and analyzing powers for $(p,n)$ reactions on ${}^{3}{\rm He}$ and ${}^{4}{\rm He}$ have been measured at a bombarding energy of $T_p$ = 346 MeV and reaction angles of $\theta_{\rm lab}$ = $9.4^{\circ}$--$27^{\circ}$. The energy transfer spectra for ${}^{3}{\rm He}(p,n)$ at large $\theta_{\rm lab}$ ($\ge$ $16^{\circ}$) are dominated by quasielastic contributions, and can be reasonably reproduced by plane-wave impulse approximation (PWIA) calculations for quasielastic scattering. By contrast, the known $L$ = 1 resonances in ${}^{4}{\rm Li}$ are clearly observed near the threshold in the ${}^{4}{\rm He}(p,n)$ spectra. Because these contributions are remarkable at small angles, the energy spectra are significantly different from those expected for quasielastic scattering. The data are compared with the PWIA calculations, and it is found that the quasielastic contributions are dominant at large $\theta_{\rm lab}$ ($\ge$ $22^{\circ}$). The nuclear correlation effects on the quasielastic peak for ${}^{4}{\rm He}(p,n)$ are also discussed.