Polarization transfer measurements for $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N (g.s.},1^+)$ at 296 MeV and nuclear correlation effects

TL;DR

This study measures polarization transfer in a nuclear reaction at 296 MeV to investigate nuclear correlations beyond the shell model, revealing discrepancies with DWIA calculations that are partly addressed by including mesonic correlations.

Contribution

The paper provides new polarization transfer data for the $^{12}C(p,n)$ reaction at 296 MeV and demonstrates the importance of nuclear correlations and mesonic effects beyond the shell model.

Findings

Significant differences between experiment and DWIA at high momentum transfer.

Inclusion of RPA response functions reduces discrepancies.

Evidence of nuclear correlations beyond the shell model.

Abstract

Differential cross sections and complete sets of polarization observables are presented for the Gamow-Teller $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N}({\rm g.s.},1^+)$ reaction at a bombarding energy of 296 MeV with momentum transfers $q$ of 0.1 to $2.2{\rm fm}^{-1}$. The polarization transfer observables are used to deduce the spin-longitudinal cross section, $ID_q$, and spin-transverse cross sections, $ID_p$ and $ID_n$. The data are compared with calculations based on the distorted wave impulse approximation (DWIA) using shell-model wave functions. Significant differences between the experimental and theoretical results are observed for all three spin-dependent $ID_i$ at momentum transfers of $q \gtrsim 0.5{\rm fm}^{-1}$, suggesting the existence of nuclear correlations beyond the shell model. We also performed DWIA calculations employing random phase approximation (RPA) response functions and found that the observed discrepancy is partly resolved by the pionic and rho-mesonic correlation effects.