SU(5)-inspired double beta decay

TL;DR

This paper explores $SU(5)$-inspired models with TeV-scale exotic particles that can contribute to neutrinoless double beta decay, unify gauge couplings without supersymmetry, and generate neutrino masses, with potential LHC observability.

Contribution

It introduces non-minimal $SU(5)$-inspired models with light exotics that explain neutrinoless double beta decay and neutrino masses without supersymmetry.

Findings

Gauge coupling unification consistent with proton decay limits.

Potential observation of colored exotics at the LHC.

Models explaining neutrino oscillations via $B-L$ violation.

Abstract

The short-range part of the neutrinoless double beta amplitude is generated via the exchange of exotic particles, such as charged scalars, leptoquarks and/or diquarks. In order to give a sizeable contribution to the total decay rate, the masses of these exotics should be of the order of (at most) a few TeV. Here, we argue that these exotics could be the "light" (i.e weak-scale) remnants of some $B-L$ violating variants of $SU(5)$. We show that unification of the standard model gauge couplings, consistent with proton decay limits, can be achieved in such a setup without the need to introduce supersymmetry. Since these non-minimal $SU(5)$-inspired models violate $B-L$, they generate Majorana neutrino masses and therefore make it possible to explain neutrino oscillation data. The "light" coloured particles of these models can potentially be observed at the LHC, and it might be possible to probe the origin of the neutrino masses with $\Delta L=2$ violating signals. As particular realizations of this idea, we present two models, one for each of the two possible tree-level topologies of neutrinoless double beta decay.