Proton-induced deuteron knockout reaction as a probe of an isoscalar proton-neutron pair in nuclei

Background: The isoscalar pn pair is expected to emerge in nuclei having the similar proton and neutron numbers but there is no clear experimental evidence for it. Purpose: We aim to clarify the correspondence between the pn pairing strength in many-body calculation and the triple differential cross section (TDX) of proton-induced deuteron knockout (p, pd) reaction on ^16O. Methods: The radial wave function of the isoscalar pn pair with respect to the center of ^16O is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation framework. The pn pairing strength V₀ in the EDF calculation is varied and the corresponding change in the TDX is investigated. Results: A clear V₀ dependence of the TDX is found for the ^16O (p, pd) ^14N (1₂^+) at 101. 3 MeV. The nuclear distortion is found to make the V₀ dependence stronger. Conclusions: Because of the clear V₀-TDX correspondence, the (p, pd) reaction will be a promising probe for the isoscalar pn pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.