$\Delta$L=2 hyperon decays induced by Majorana neutrinos and doubly-charged scalars

TL;DR

This paper investigates hyperon decays violating lepton number by two units, analyzing both long-range Majorana neutrino effects and short-range scalar contributions, to better understand neutrino nature and potential new physics signals.

Contribution

It provides a comprehensive calculation of hyperon $ o$ hyperon di-lepton decay rates including form factors and explores new scenarios with heavy Majorana neutrinos and scalar bosons.

Findings

Finite decay rate predictions with form factors in the Majorana neutrino model

Enhanced decay rates in low-scale seesaw scenarios with two heavy neutrinos

Additional decay channels induced by scalar bosons

Abstract

Searches for $\Delta L=2$ decays are crucial to disentangle the Dirac vs Majorana nature of neutrinos. While neutrinoless nuclear double beta decays are the most promising tool to look for di-electron signals of $\Delta L=2$, searches of di-lepton channels with other flavors are far less limited by statistics. We revisit the calculation of $\Delta L=2$ decays of hyperons $B^-_i\to B^+_f\ell^-\ell'^-$. We compute the rates of these decays by including the hyperon form factors, which yields finite results in the one-loop model mechanism involving Majorana neutrinos (long-range contributions). In addition, we study the short-range contributions to these kinds of processes in two appealing scenarios. First, we consider the effects of heavy Majorana neutrinos in low-scale seesaw models that involve a minimal parametrization with only two heavy Majorana states. Second, we study an alternative model where $\Delta L=2$ decays are induced by a scalar boson coupled to di-leptons to provide additional predictions.