Pairing correlations, influencing almost every feature of ground and low-lying states in nuclei, lie at the heart of nuclear physics. Understanding the mechanism of neutron-proton (np) pairing in N=Z nuclei has been a long-sought goal in nuclear structure since the early sixties. Despite large efforts in both theoretical and experimental studies, the fundamental nature and the interplay between T=0 and T=1 pairs are still the subject of debate. Cross section measurement of np-pair transfer is considered as a sensitive probe for the insight into T=0 and T=1 np pairing collectivity and its mechanism [1-3].
We therefore carried out systematic np-transfer measurements spanning N=Z sd-shell nuclei using (p,3He) and (3He,p) reactions at RCNP Osaka University. 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. In this talk, we will present this work .
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