The ScotoSinglet Model: a scalar singlet extension of the Scotogenic Model

Ankit Beniwal,Anthony G Williams,Nicholas Leerdam,Martin White,Juan Herrero-García

doi:10.1007/jhep06(2021)136

Abstract

The Scotogenic Model is one of the most minimal models to account for both neutrino masses and dark matter (DM). In this model, neutrino masses are generated at the one-loop level, and in principle, both the lightest fermion singlet and the lightest neutral component of the scalar doublet can be viable DM candidates. However, the correct DM relic abundance can only be obtained in somewhat small regions of the parameter space, as there are strong constraints stemming from lepton flavour violation, neutrino masses, electroweak precision tests and direct detection. For the case of scalar DM, a sufficiently large lepton-number-violating coupling is required, whereas for fermionic DM, coannihilations are typically necessary. In this work, we study how the new scalar singlet modifies the phenomenology of the Scotogenic Model, particularly in the case of scalar DM. We find that the new singlet modifies both the phenomenology of neutrino masses and scalar DM, and opens up a large portion of the parameter space of the original model.

Highlights

The origin of light neutrino masses and dark matter (DM) remain unsolved puzzles of the Standard Model (SM)
The correct DM relic abundance can only be obtained in somewhat small regions of the parameter space, as there are strong constraints stemming from lepton flavour violation, neutrino masses, electroweak precision tests and direct detection
The ScotoSinglet Model (ScSM) permits both scalar and fermionic DM candidates, but we focus on the case of scalar DM for two reasons: 1. The fermion DM case is very similar to the usual Scotogenic Model (ScM) where strong constraints from lepton flavour violation (LFV) exist on the Yukawa couplings

Summary

Introduction

The origin of light neutrino masses and dark matter (DM) remain unsolved puzzles of the Standard Model (SM). As for DM, a GeV–TeV scale Weakly Interacting Massive Particle, stabilised by some remanent symmetry (e.g., Z2), provides an elegant solution In this context, the Scotogenic Model (ScM), first proposed by Ernest Ma (2006) [3] [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]), emerges as one of the simplest joint solutions for neutrino masses and DM It adds a new scalar doublet Φ and new Majorana singlets ψi (i ≥ 2), all of them charged under a Z2 symmetry. Another interesting variant has been recently proposed where the Z2 symmetry is exchanged for a U(1) symmetry; it is referred to as the Generalised Scotogenic Model (GScM) [20]

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Results

Conclusion