Chiral perturbation theory calculation for pn -> dpipi at threshold

TL;DR

This paper presents a comprehensive leading-order Chiral Perturbation Theory calculation of the pn -> dpipi reaction near threshold, including nucleon-nucleon interactions, to better understand non-resonant two-pion production in nucleon collisions.

Contribution

It provides the first complete leading-order calculation of the reaction, incorporating nucleon-nucleon interactions consistently, and identifies important diagrams previously overlooked.

Findings

Leading order contributions behave as expected by power counting.

Nucleon-nucleon interactions are crucial and significantly affect the results.

Identifies key diagrams of equal importance to those in earlier works.

Abstract

We investigate the reaction pn -> dpipi in the framework of Chiral Perturbation Theory. For the first time a complete calculation of the leading order contributions is presented. We identify various diagrams that are of equal importance as compared to those recognized in earlier works. The diagrams at leading order behave as expected by the power counting. Also for the first time the nucleon-nucleon interaction in the initial, intermediate and final state is included consistently and found to be very important. This study provides a theoretical basis for a controlled evaluation of the non-resonant contributions in two-pion production reactions in nucleon-nucleon collisions.