Symmetryless Dark Matter

TL;DR

This paper explores models where dark matter stability is maintained despite flavor symmetry breaking, proposing minimal scenarios with potential LHC testability and hierarchical Yukawa couplings.

Contribution

It identifies conditions for stable dark matter with broken flavor symmetry, using Higgs as flavons and analyzing the impact of flavon VEVs on dark matter stability.

Findings

Certain scalar and fermion multiplets can remain stable without dangerous decay operators.

Using Higgs as flavons allows electroweak scale flavon VEVs.

Models predict testable signatures at the LHC.

Abstract

It is appealing to stabilize dark matter by the same discrete symmetry that is used to explain the structure of quark and lepton mass matrices. However, to generate the observed fermion mixing patterns, any flavor symmetry must necessarily be broken, rendering dark matter unstable. We study singlet, doublet and triplet SU(2) multiplets of both scalar and fermion dark matter candidates and enumerate the conditions under which no d < 6 dark matter decay operators are generated even in the case if the flavor symmetry is broken to nothing. We show that the VEVs of flavon scalars transforming as higher multiplets (e.g. triplets) of the flavor group must be at the electroweak scale. The most economical way for that is to use SM Higgs boson(s) as flavons. Such models can be tested by the LHC experiments. This scenario requires the existence of additional Froggatt-Nielsen scalars that generate hierarchies in Yukawa couplings. We study the conditions under which large and small flavor breaking parameters can coexist without destabilizing the dark matter.