Nucleon decays into three leptons: contact contributions

TL;DR

This paper investigates contact contributions from dimension-9 operators to baryon number violating nucleon decays into three leptons, providing a comprehensive theoretical framework and experimental constraints.

Contribution

It systematically constructs and analyzes dimension-9 operators, matching them to chiral perturbation theory and connecting to UV models for experimental predictions.

Findings

Derived constraints on dimension-9 operators from experimental data

Constructed a complete basis of relevant dimension-9 operators

Connected UV models to effective field theory framework

Abstract

Baryon number violating (BNV) nucleon decays into three leptons provide a unique probe of BNV interactions beyond the conventional two-body modes involving a single lepton and a light meson. In a previous work [Nucleon decays into three leptons: noncontact contributions, arXiv:2512.02692.], two of us analyzed the noncontact contributions to these decays arising from dimension-6 (dim-6) operators within the low-energy effective field theory (LEFT), and found that they are severely suppressed due to stringent constraints on these dim-6 operators. In this work, we continue this endeavor by systematically investigating the contact contributions originating from dim-9 LEFT operators. We construct a complete basis of dim-9 operators relevant to these processes, and subsequently match them onto chiral perturbation theory to calculate their decay widths. By employing existing experimental data, we derive stringent constraints on the relevant operators. In addition, we present the analysis of an ultraviolet-complete model to demonstrate its connection with our theoretical framework, thereby facilitating further studies of these exotic nucleon decays in upcoming neutrino experiments with large fiducial masses.