Abstract

Many minimal models of dark matter (DM) or canonical solutions to the hierarchy problem are either excluded or severely constrained by LHC and direct detection null results. In particular, Higgs Portal Dark Matter (HPDM) features a scalar coupling to the Higgs via a quartic interaction, and obtaining the measured relic density via thermal freeze-out gives definite direct detection predictions which are now almost entirely excluded. The Twin Higgs solves the little hierarchy problem without coloured top partners by introducing a twin sector related to the Standard Model (SM) by a discrete symmetry. We generalize HPDM to arbitrary Twin Higgs models and introduce Twin Higgs Portal Dark Matter (THPDM), which features a DM candidate with an SU(4)-invariant quartic coupling to the Twin Higgs scalar sector. Given the size of quadratic corrections to the DM mass, its most motivated scale is near the mass of the radial mode. In that case, DM annihilation proceeds with the full Twin Higgs portal coupling, while direct detection is suppressed by the pNGB nature of the 125 GeV Higgs. For a standard cosmological history, this results in a predicted direct detection signal for THPDM that is orders of magnitude below that of HPDM with very little dependence on the precise details of the twin sector, evading current bounds but predicting possible signals at next generation experiments. In many Twin Higgs models, twin radiation contributions to ∆Neff are suppressed by an asymmetric reheating mechanism. We study this by extending the νMTH and X MTH models to include THPDM and compute the viable parameter space according to the latest CMB bounds. The injected entropy dilutes the DM abundance as well, resulting in additional suppression of direct detection below the neutrino floor.

Highlights

  • The most important contributions to the Higgs potential come from top quark loops

  • dark matter (DM) annihilation proceeds with the full Twin Higgs portal coupling, while direct detection is suppressed by the pseudo-Nambu Goldstone bosons (pNGBs) nature of the 125 GeV Higgs

  • We study this by extending the νMTH and XMTH models to include Twin Higgs Portal Dark Matter (THPDM) and compute the viable parameter space according to the latest CMB bounds

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Summary

Twin Higgs Models

Twin Higgs models solve the little hierarchy problem through the introduction of a twin sector of new particles, whose structure is related by a discrete symmetry to the structure of the Standard Model. The absence of light twin degrees of freedom can lead to the presence of long-lived particles in the twin spectrum, such as twin glueballs or twin bottomonium in the FTH [21] These states can only decay through the small Higgs portal coupling that is required by naturalness, making them meta-stable. After briefly reviewing scalar Higgs Portal Dark Matter, we study the phenomenology of THPDM first by assuming standard cosmological history in section 4 for two extreme cases of twin sectors, FTH-like and MTH-like. The former is the most minimal twin sector that can solve the little hierarchy problem, while the latter is a stand-in for a TH construction with the smallest hard Z2-breaking necessary to solve the ∆Neff problem.

Scalar Higgs portal dark matter
Pseudo-Goldstone suppression of direct detection
Direct detection predictions for THPDM
Natural mass of twin Higgs portal scalar dark matter
Asymmetrically reheated twin Higgs portal dark matter
Review of standard mirror twin higgs cosmological history
Review of asymmetric reheating mechanism
Dark matter dilution
THPDM direct detection with asymmetric reheating
Findings
Conclusion
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