Spontaneous twin symmetry breaking

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.

Section: Jhep08(2021)009mentioning

confidence: 99%

Twin Higgs portal dark matter

Curtin

Gryba

2021

“…It is therefore necessary to introduce a small breaking of the Z 2 symmetry to achieve a phenomenologically viable vacuum alignment. This is typically done by hand through soft or hard explicit Z 2 breaking interactions, but it is appealing to find a dynamical origin of this Z 2 breaking, which has been explored in [14,17,[59][60][61]. The efficiency of our simple construction is that the Φ B VEV provides an automatic source of spontaneous Z 2 breaking, which is sufficient to align the vacuum in the desired way.…”

Section: Hypercharge Scalar Dynamicsmentioning

confidence: 99%

“…At the same time, a soft-breaking of the discrete symmetry is essential for successful twin Higgs phenomenology. While mechanisms for spontaneously generating Z 2 breaking in the Higgs sector have been explored [14,17,[59][60][61], it is appealing to have a dynamical origin of Z 2 breaking in both the Higgs potential and the twin spectrum. In this work we extend the exactly Z 2 symmetric MTH by a hypercharged scalar and its twin.…”

Section: Introductionmentioning

confidence: 99%

Breaking mirror twin hypercharge

Batell

Verhaaren

2019

The Twin Higgs scenario stabilizes the Higgs mass through an approximate global symmetry and has remained natural in the face of increasingly stringent LHC bounds on colored top partners. Two basic structural questions in this framework concern the nature of the twin hypercharge gauge symmetry and the origin of the Z 2 symmetry breaking needed to achieve the correct vacuum alignment. Both questions are addressed in a simple extension of the Mirror Twin Higgs model with an exact Z 2 symmetry and a scalar field that spontaneously breaks both twin hypercharge and Z 2. Due to the Z 2 symmetry and an approximate U(2) symmetry in the potential, a new hypercharge scalar appears in the visible sector and, like the Higgs, is a pseudo-Nambu-Goldstone boson with a weak-scale mass. Couplings between the hypercharge scalar and matter provide a new dynamical source of twin sector fermion masses. Depending on the nature and size of these couplings, a variety of experimental signatures may arise, including quark and lepton flavor violation, neutrino masses and mixings as well as direct collider probes of the hypercharged scalar. These signals are correlated with the twin matter spectrum, which can differ dramatically from the visible one, including dynamical realizations of fraternal-like scenarios.

“…It is appealing to have a dynamical origin for these soft and/or hard Z 2 breaking mechanisms. One possibility is that the Z 2 is an exact symmetry of the theory but is spontaneously broken [49][50][51][52][53]. Such spontaneous Z 2 breaking could result from a pattern of gauge symmetry breaking in the mirror sector that differs from the SM's electroweak symmetry breaking pattern.…”

Section: Introductionmentioning

confidence: 99%

Breaking mirror twin color

Batell

Verhaaren

2020

We investigate simple extensions of the Mirror Twin Higgs model in which the twin color gauge symmetry and the discrete Z 2 mirror symmetry are spontaneously broken. This is accomplished in a minimal way by introducing a single new colored triplet, sextet, or octet scalar field and its twin along with a suitable scalar potential. This spontaneous Z 2 breaking allows for a phenomenologically viable alignment of the electroweak vacuum, and leads to dramatic differences between the visible and mirror sectors with regard to the residual gauge symmetries at low energies, color confinement scales, and particle spectra. In particular, several of our models feature a remnant SU(2) or SO(3) twin color gauge symmetry with a very low confinement scale in comparison to Λ QCD. Furthermore, couplings between the colored scalar and matter provide a new dynamical source of twin fermion masses, and due to the mirror symmetry, these lead to a variety of correlated visible sector effects that can be probed through precision measurements and collider searches.