Baryon-number-violating nucleon decays in ALP effective field theories

TL;DR

This paper investigates how axion-like particles (ALPs) can induce baryon-number-violating nucleon decays within effective field theories, providing new insights into potential signals of physics beyond the Standard Model in future experiments.

Contribution

It develops a comprehensive EFT framework for ALP-induced baryon-number violation, including decay signatures and experimental constraints, extending previous models with detailed chiral perturbation theory matching.

Findings

Derived effective chiral Lagrangian for ALP-baryon interactions

Identified decay channels and kinematic signatures of ALP-induced nucleon decays

Set constraints on UV scale from existing experimental searches

Abstract

The search for baryon-number-violating (BNV) nucleon decay is an intriguing probe of new physics beyond the SM in future neutrino experiments with enhanced sensitivity. The dark sector states such as an axion or axion-like particle (ALP) can induce nucleon decays with distinct signature and kinematics from the conventional nucleon decays. In this work, we study the ALP effective field theories (EFTs) with baryon number violation and the impact of light ALP on BNV nucleon decays. We revisit the dimension-8 BNV operators in the extended EFTs with an ALP field $a$ respecting shift symmetry. The low-energy EFT operators with $|\Delta (B-L)|=2$ and $|\Delta (B-L)|=0$ are matched to the baryon chiral perturbation theory. We obtain the effective chiral Lagrangian and the BNV interactions between ALP and baryons/mesons. The ALP interactions lead to two-body baryon decays $B\to \ell~({\rm or}~\nu)~a$ and three-body nucleon decays $N\to M~\ell~({\rm or}~\nu)~a$. We obtain the constraints on the UV scale from the invisible $\Lambda^0$ decay search at BESIII, the invisible neutron decay search at KamLAND and proton decay search at Super-K. We also show the projections of some other baryon/nucleon decays and present the distinct distributions of kinematic observable.