Importance of theD-State Probability of the Deuteron in Thresholdp+p→π+d

Using a number of realistic, local and nonlocal, separable two-nucleon interactions, it is shown that threshold $s$-wave pion production is sensitive to the $D$-state probability of the deuteron and the nonlocality of the interaction. This enables one to use the reaction $p+p\to {\pi }^{+}+d$ to study the relative strength of the central to tensor potential and the nonlocality of the nucleon-nucleon interaction at short distances.