Charge Symmetry Breaking in the n p --> d pi^0 reaction

TL;DR

This paper uses Heavy Baryon Chiral Perturbation Theory to calculate charge symmetry breaking effects in the n p --> d pi^0 reaction, comparing theoretical predictions with experimental data.

Contribution

It applies recent power counting methods to asymmetry calculations and examines diagram reducibility, providing updated theoretical insights.

Findings

The theory over-predicts the asymmetry across various parameters.

Recent power counting successfully describes total cross sections.

Diagram reducibility is analyzed in the context of leading order contributions.

Abstract

The asymmetry in the angular distribution of n p --> d pi^0 due to Charge Symmetry Breaking is calculated using Heavy Baryon Chiral Perturbation Theory. Recent developments in power counting have proven successful in describing total cross sections, and we apply them to the asymmetry calculation. Reducibility in one of the leading order diagrams is examined. We compare the updated theory with experimental results for a range of physically reasonable parameters and find over-prediction for the entire range.