The D coefficient in neutron beta decay in effective field theory

TL;DR

This paper uses effective field theory to analyze the D coefficient in neutron beta decay, providing precise calculations of electromagnetic contributions and extending its potential to probe new physics beyond the Standard Model.

Contribution

It introduces a heavy-baryon effective field theory approach to calculate the D coefficient, including higher-order corrections and electromagnetic effects, with improved accuracy.

Findings

Electromagnetic contributions vanish in the heavy-baryon limit.

Leading correction to the D coefficient is accurate to better than 1%.

The results extend the use of the D coefficient in new physics searches.

Abstract

In this paper we explore the time-reversal-odd triple-correlation coefficient in neutron beta decay, the so-called "D coefficient", using heavy-baryon effective field theory with photon degrees of freedom. We find that this framework allows us to reproduce the known results for the contribution which comes from final-state interactions, and also to discuss higher-order corrections. In particular we are able to show that in the heavy-baryon limit all electromagnetic contributions vanish. By calculating the leading correction to the known result, we give a final expression which is accurate to better than 1%. Hence we extend downwards the range over which the D coefficient could be used to explore time-violation from new physics.