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.
We report measurements of the cross-section and a complete set of polarization transfer coefficients for the ${}^{3}{rm He}(p,n)$ reaction at a bombarding energy $T_p$ = 346 MeV and a reaction angle $theta_{rm lab}$ = $0^{circ}$. The data are compa
red with the corresponding free nucleon-nucleon values on the basis of the predominance of quasi-elastic scattering processes. Significant discrepancies have been observed in the polarization transfer $D_{LL}(0^{circ})$, which are presumably the result of the three-proton $T$ = 3/2 resonance. The spin--parity of the resonance is estimated to be $1/2^-$, and the distribution is consistent with previous results obtained for the same reaction at $T_p$ = 48.8 MeV.
We report measurements of the cross section and a complete set of polarization observables 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. The data are compared with disto
rted wave impulse approximation calculations employing transition form factors normalized to reproduce the observed beta-decay $ft$ value. The cross section is significantly under-predicted by the calculations at momentum transfers $q gtrsim $ 0.5 ${rm fm^{-1}}$. The discrepancy is partly resolved by considering the non-locality of the nuclear mean field. However, the calculations still under-predict the cross section at large momentum transfers of $q$ $simeq$ 1.6 ${rm fm^{-1}}$. We also performed calculations employing random phase approximation response functions and found that the observed enhancement can be attributed in part to pionic correlations in nuclei.
A complete set of polarization transfer observables has been measured for the $^{12}{rm C}(p,n)$ reaction at $T_p=296 {rm MeV}$ and $theta_{rm lab}=0^{circ}$. The total spin transfer $Sigma(0^{circ})$ and the observable $f_1$ deduced from the measure
d polarization transfer observables indicate that the spin--dipole resonance at $E_x simeq 7 {rm MeV}$ has greater $2^-$ strength than $1^-$ strength, which is consistent with recent experimental and theoretical studies. The results also indicate a predominance of the spin-flip and unnatural-parity transition strength in the continuum. The exchange tensor interaction at a large momentum transfer of $Q simeq 3.6 {rm fm}^{-1}$ is discussed.
