Twin Higgs portal dark matter

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.

Quantum collider probes of the fermionic Higgs portal

“…In Appendix D we consider different non-zero initial conditions C 6 (µ * ) and C H□ (µ * ). Notice that the chosen f corresponds to the minimal value in twin-Higgs models that is consistent with existing experimental measurement, necessitating v/ f ≲ 1/3 [73]. Since the tuning amounts to roughly 2v 2 / f 2 in minimal twin-Higgs models [38,74] the choice of f = 3v implies only a very modest tuning of around 20% -we repeat our study for a more tuned twin-Higgs model in Appendix B.…”

The Physics of Light Relics

“…Assuming that the universe reheated above this temperature with otherwise typical cosmological evolution, the energy density in mirror photons and neutrinos corresponds to Δ𝑁 eff ≈ 5.6, such that the simplest mirror Twin Higgs is badly excluded by current bounds on Δ𝑁 eff . There are then two broad possibilities consistent with current bounds: either the Twin sector is not an exact mirror copy (such that the Twin partners of the photon and neutrinos are heavy or decoupled [150][151][152]), or the energy densities in the Standard Model and Twin sector differ significantly in the early universe [96,97,153]. While the former possibility can be arranged, it requires understanding why the ℤ 2 symmetry is good for particles that couple strongly to the Higgs but bad for particles that do not.…”

Cosmology of the Twin Higgs without explicit $\mathbb{Z}_2$ breaking

“…At the same time, the Twin Higgs model can be consistent with cosmology, which is already the subject of a considerable literature [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. 1 In a similar fashion to the Higgs signal strengths, the cosmology of the Twin Higgs also requires Z 2 breaking.…”