Hints of Standard Model Higgs Boson at the LHC and Light Dark Matter Searches

TL;DR

The paper discusses potential hints of a 125 GeV Higgs boson at the LHC and explores implications for light dark matter models, especially Higgs-portal scenarios with isospin-violating interactions, considering experimental constraints and model extensions.

Contribution

It introduces a two-Higgs-doublet model with a scalar dark matter candidate that can reconcile Higgs hints with light dark matter constraints and isospin violation.

Findings

Hints of a 125 GeV Higgs at the LHC are consistent with SM expectations.

A Higgs-portal dark matter model can accommodate light DM with isospin-violating interactions.

Model extensions are needed if future data confirms the Higgs signals.

Abstract

The most recent results of searches at the LHC for the Higgs boson h have turned up possible hints of such a particle with mass m_h about 125 GeV consistent with standard model (SM) expectations. This has many potential implications for the SM and beyond. We consider some of them in the contexts of a simple Higgs-portal dark matter (DM) model, the SM plus a real gauge-singlet scalar field D as the DM candidate, and a couple of its variations. In the simplest model with one Higgs doublet and three or four generations of fermions, for D mass m_D < m_h/2 the invisible decay h -> DD tends to have a substantial branching ratio. If future LHC data confirm the preliminary Higgs indications, m_D will have to exceed m_h/2. To keep the DM lighter than m_h/2, one will need to extend the model and also satisfy constraints from DM direct searches. The latter can be accommodated if the model provides sizable isospin violation in the DM-nucleon interactions. We explore this in a two-Higgs-doublet model combined with the scalar field D. This model can offer a 125-GeV SM-like Higgs and a light DM candidate having isospin-violating interactions with nucleons at roughly the required level, albeit with some degree of fine-tuning.