Deuteron is the only binding system which consists of two nucleons (a proton and a neutron) in free space.
Recently, theoretical calculation with density functional theory (DFT) suggests that the "deuteron-like" pn pair exists in nuclei.
We propose the (p,pd) reaction to probe the pn pair, and discuss how the (p,pd) cross section reflects the pn pair inside the target nucleus.
We calculate the cross section employing the transition density calculated with DFT. The results are compared with those obtained with assuming a deuteron "cluster" a priori.