Parity-violating polarization in $np \to d\gamma$ with a pionless effective field theory

TL;DR

This paper develops a pionless effective field theory with dibaryon fields to analyze parity-violating effects in neutron-proton capture, providing a new theoretical framework for weak interactions in few-body nuclear systems.

Contribution

It introduces a pionless EFT with dibaryon fields to calculate parity violation in np capture, including unknown weak couplings, and compares results with hybrid calculations.

Findings

Calculated parity-violating observable at threshold

Expressed results linearly in unknown couplings

Discussed extension to other few-body systems

Abstract

We consider the two-nucleon weak interaction with a pionless effective field theory. Dibaryon fields are introduced to facilitate calculations and ensure precision in the initial and final state propagators. Weak interactions are accounted for with the parity-violating dibaryon-nucleon-nucleon vertices, which contain unknown weak dibaryon-nucleon-nucleon coupling constants. We apply the model to the calculation of a parity-violating observable in the neutron-proton capture at threshold. Result is obtained up to the linear order in the unknown dibaryon-nucleon-nucleon coupling constants. We compare our result to the one obtained from a hybrid calculation, and discuss the extension to weak interactions in the few-body systems.