Reviving sub-TeV $SU(2)_L$ lepton doublet Dark Matter

TL;DR

This paper explores a hybrid dark matter production mechanism involving both thermal and non-thermal processes in a model with an $SU(2)_L$ lepton doublet and a singlet scalar, allowing for viable sub-TeV dark matter candidates.

Contribution

It introduces a novel hybrid dark matter production scenario with a specific $SU(2)_L$ lepton doublet and scalar model, addressing under-abundance and detection constraints.

Findings

Lepton doublet pseudo-Dirac DM with 450-1200 GeV mass is viable.

Non-thermal production from scalar decay helps achieve correct relic density.

Model evades direct detection constraints via an $SU(2)_L$ triplet scalar.

Abstract

In this work we study the hybrid kind of dark matter(DM) production mechanism where both thermal and non-thermal contribution at two different epochs set the DM relic abundance. This hybrid set up in turn shifts the parameter space of DM in contrast to pure thermal DM scenario. We review such production mechanism in the context of the $SU(2)_L$ lepton doublet dark matter ($\Psi$) augmented with an additional singlet dark scalar ($S$). The neutral component of the dark doublet can serve as a stable DM candidate and in pure thermal scenario, it is under-abundant as well as excluded from direct detection constraints due to its strong gauge interactions in the sub-TeV mass regime. However, in addition to the thermal contribution, the late time non-thermal DM production from the decay of the long-lived dark scalar $S$ helps to fulfill the deficit in DM abundance. On the other hand, the strong gauge mediated direct detection constraint can be evaded with the help of a $SU(2)_L$ triplet scalar(with $Y=2$), resulting a pseudo-Dirac DM. To realize our proposed scenario we impose a discrete $\mathcal{Z}_2$ symmetry under which both $\Psi$ and $S$ are odd while rest of the fields are even. We find the lepton doublet pseudo-Dirac DM with mass $\sim 450-1200$ GeV, compatible with the observed relic density, direct, indirect, and existing collider search constraints.