Neutrinoless quadruple beta decay

Abstract

We point out that lepton number violation is possible even if neutrinos are Dirac particles. We illustrate this by constructing a simple model that allows for lepton number violation by four units only. As a consequence, neutrinoless double beta decay is forbidden, but neutrinoless quadruple beta decay is possible: (A, Z) → (A, Z +4)+4 e − . We identify three candidate isotopes for this decay, the most promising one being 150 Nd due to its high Q 0ν4β -value of 2 MeV. Analogous processes, such as neutrinoless quadruple electron capture, are also possible. The expected lifetimes are extremely long, and experimental searches are challenging.

The $$B-L$$ B - L scotogenic models for Dirac neutrino masses

“…One is responsible for the absence of SM Yukawa couplingsν L ν R φ 0 and the other for the stability of intermediate fields as dark matter (DM). The symmetries could be the discrete ones Z 2 [47,53,54], Z 3 [50,55], or Z 4 [56,57].…”

A two-Higgs-doublet model facing experimental hints

“…The same Barr-Zee diagrams that give the desired Δa μ also lead to τ → μγ decays in case 32 0 (as required for h → μτ). If we want to explain h → μτ, the τ → μγ rate needs to be tuned to small values using m H m A , which necessarily also suppresses the contribution to Δa μ (see Fig 2).…”

Four and two-lepton signals of leptophilic gauge interactions at large colliders

“…Although the kinetic mixing may receive small quantum corrections, its size can be large at low energy due to the matching with a more fundamental theory at high scale, hence making the phenomenological analysis compulsory. Finally, the SM extension with an extra gauge boson coupled to L µ − L τ has been recently invoked to explain small discrepancies in Higgs and B decays [24], although the proposed models include extra matter and assumptions beyond the phenomenological analysis performed here. Leptophilic interactions have been also considered to produced and annihilate dark matter [25].…”