Covariant approach to allowed beta decay
Abstract
We propose a Lorentz-covariant on-shell formalism for allowed nuclear beta decay. Nuclear matrix elements are organized in a systematic effective field theory expansion in the recoil momentum, with the dependence on nuclear spin and polarization encoded in little-group-covariant structures. In this language, we construct the most general standard and exotic currents for allowed transitions through first recoil order. We then derive the differential decay distribution encoded in a set of Lorentz-invariant form factors. Specializing to the rest frame of the parent nucleus, we relate our parameters to those used in the traditional beta-decay literature and in nucleon- and quark-level effective field theories. The formalism provides a natural framework for extensions to higher recoil orders, radiative corrections, and forbidden transitions.
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BibTeX
@misc{cruzalzaga2026covariant,
title = {{Covariant approach to allowed beta decay}},
author = {Sergio Cruz-Alzaga and Adam Falkowski},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.18062},
eprint = {2610.18062},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05842400v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Covariant approach to allowed beta decay
AU - Sergio Cruz-Alzaga
AU - Adam Falkowski
PY - 2026
DA - 2026/10/13
PB - HAL
DO - 10.48550/arxiv.2610.18062
UR - https://hal.science/hal-05842400v1
AB - We propose a Lorentz-covariant on-shell formalism for allowed nuclear beta decay. Nuclear matrix elements are organized in a systematic effective field theory expansion in the recoil momentum, with the dependence on nuclear spin and polarization encoded in little-group-covariant structures. In this language, we construct the most general standard and exotic currents for allowed transitions through first recoil order. We then derive the differential decay distribution encoded in a set of Lorentz-invariant form factors. Specializing to the rest frame of the parent nucleus, we relate our parameters to those used in the traditional beta-decay literature and in nucleon- and quark-level effective field theories. The formalism provides a natural framework for extensions to higher recoil orders, radiative corrections, and forbidden transitions.
ER -