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 O16. Methods: The radial wave function of the isoscalar pn pair with respect to the center of O16 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 O16(p,pd)N14(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.