Nucleon Decay into Dark Sector

TL;DR

This paper explores how nucleon decay into a dark sector fermion could reveal new physics, with unique signatures that might have been missed by traditional searches, and discusses the role of light mediators in these processes.

Contribution

It introduces the possibility of nucleon decay into dark sector particles mediated by high-scale physics and light vectors, highlighting new search avenues for dark matter.

Findings

Dark sector fermion X can cause nucleon decay with distinctive signatures.

Neutron decay into X and Z_d can be significant depending on parameters.

Dark force mediated by Z_d leads to observable decay products like lepton pairs.

Abstract

A sub-GeV dark sector fermion X can have baryon number violating interactions induced by high scale physics, leading to nucleon decay into X + meson and neutron -> X + photon. Such processes can mimic standard search modes containing a neutrino, but have different kinematics and may have escaped detection. If a dark force mediated by a light vector Z_d acts on X, depending on parameters, neutron -> X + Z_d can be important. In typical scenarios, Z_d decays into l^+l^-, where l=e, mu, with order unity branching fraction. Nucleon decay searches can potentially uncover new dark states that are otherwise inaccessible, due to their negligible coupling to ordinary matter or cosmological abundance.