Investigating neutron-proton pairing in s d -shell nuclei via ( p , He 3 ) and ( He 3 , p ) transfer reactions

Neutron-proton pairing correlations are investigated in detail via $np$ transfer reactions in $N=Z\phantom{\rule{4pt}{0ex}}sd$-shell nuclei. In particular, we study the cross-section ratio of the lowest ${0}^{+}$ and ${1}^{+}$ states as an observable to quantify the interplay between $T=0$ (isoscalar) and $T=1$ (isovector) pairing strengths. The experimental results are compared to second-order distorted-wave Born approximation calculations with proton-neutron amplitudes obtained in the shell-model formalism using the universal $sd$-shell interaction B. Our results suggest underestimation of the nonneglible isoscalar pairing strength in the shell-model descriptions at the expense of the isovector channel.