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

TL;DR

This paper investigates the effectiveness of chiral perturbation theory in connecting different nuclear reactions, revealing limitations at leading order and the need for higher-order calculations to match experimental data.

Contribution

The study demonstrates that leading-order chiral operators fail to reproduce experimental amplitudes, highlighting the necessity of including higher-order terms for accurate reaction modeling.

Findings

Leading-order chiral operators do not match experimental p-wave pi-production data.

Including higher-order counter terms improves agreement with experimental energy dependence.

Bridging reactions with different kinematics requires higher-order calculations for accuracy.

Abstract

We focus on a powerful aspect of chiral perturbation theory (chi PT) which provides us with a ``bridge'' over different reactions. For this purpose, we study a contact operator which contributes p-wave pi-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\to de^+\nu_e), and then calculate the partial wave amplitude (a_0) for the p-wave pi-production (pp\to pn\pi^+). We find that the chiral operator including the contact term does not reproduce a_0 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 a_0 is then consistent with the data.