Majorana dark matter through the Higgs portal under the vacuum stability lamppost

TL;DR

This paper investigates a Higgs portal model with Majorana dark matter candidates, analyzing vacuum stability, relic abundance, and experimental constraints, identifying parameter regions compatible with all conditions up to the Planck scale.

Contribution

It demonstrates the existence of a parameter space where Majorana dark matter and vacuum stability coexist up to the Planck scale, with testable predictions for direct detection.

Findings

Stable vacuum up to the Planck scale is achievable.

Dark matter mass range 350 GeV to 1 TeV is viable.

Parameter space aligns with current and near-future direct detection experiments.

Abstract

We study the vacuum stability of a minimal Higgs portal model in which the standard model (SM) particle spectrum is extended to include one complex scalar field and one Dirac fermion. These new fields are singlets under the SM gauge group and are charged under a global U(1) symmetry. Breaking of this U(1) symmetry results in a massless Goldstone boson, a massive CP-even scalar, and splits the Dirac fermion into two new mass-eigenstates, corresponding to Majorana fermions. The lightest Majorana fermion (w) is absolutely stable, providing a plausible dark matter (DM) candidate. We show that interactions between the Higgs sector and the lightest Majorana fermion which are strong enough to yield a thermal relic abundance consistent with observation can easily destabilize the electroweak vacuum or drive the theory into a non-perturbative regime at an energy scale well below the Planck mass. However, we also demonstrate that there is a region of the parameter space which develops a stable vacuum (up to the Planck scale), satisfies the relic abundance, and is in agreement with direct DM searches. Such an interesting region of the parameter space corresponds to DM masses 350 GeV \alt m_w \alt 1 TeV. The region of interest is within reach of second generation DM direct detection experiments.