Derivation of Dark Matter Parity from Lepton Parity

TL;DR

This paper demonstrates that in certain extensions of the standard model, lepton parity conservation naturally leads to stable dark matter, and introduces a radiative Type II seesaw model with distinctive decay signatures of the doubly charged Higgs.

Contribution

It reveals that lepton parity can ensure dark matter stability in models with broken lepton number and proposes a new radiative Type II seesaw model with unique phenomenology.

Findings

Lepton parity conservation implies dark matter stability without extra symmetries.

The new model predicts the doubly charged Higgs decays predominantly into W^+W^+.

Application to existing models shows consistent dark matter and neutrino mass generation.

Abstract

It is shown that in extensions of the standard model of quarks and leptons where additive lepton number $L$ is broken by two units, so that $Z_2$ lepton parity, i.e. $(-1)^L$ which is either even or odd, remains exactly conserved, there is the possibility of stable dark matter without additional symmetry. This applies to many existing simple models of Majorana neutrino mass with dark matter, including some radiative models. Several well-known examples are discussed. This new insight leads to the construction of a radiative Type II seesaw model of neutrino mass with dark matter where the dominant decay of the doubly charged Higgs boson $\xi^{++}$ is into $W^+W^+$ instead of the expected $l_i^+ l_j^+$ lepton pairs for the well-known tree-level model.