Bridging over p-wave π-production and weak processes in few-nucleon systems with chiral perturbation theory

We focus on a powerful aspect of chiral perturbation theory (χPT) which provides us with a “bridge” over different reactions. For this purpose, we study a contact operator which contributes p-wave π-production and several weak processes. We fix the unknown coupling of the contact operator using a matrix element of a low-energy weak process (pp → deνe), and then calculate the partial wave amplitude (a0) for the p-wave π-production (pp → pnπ). We find that the chiral operator including the contact term does not reproduce a0 extracted from data, showing that the bridging over reactions with significantly different kinematics is not necessarily successful. We argue the importance of a specific higher order calculation. In order to gain an insight into a higher order calculation, we consider a higher order counter term, and find that the energy dependence of a0 is then consistent with the data.