Minimal mirror twin Higgs

Abstract

In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC reach. We show that consistency with observations requires that the Z 2 parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole Z 2 breaking, can generate the Z 2 breaking in the Higgs sector necessary for the Twin Higgs mechanism. The theory has constrained and correlated signals in Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments, over a region of parameter space where the fine-tuning for the electroweak scale is 10-50%. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional Z 2 breaking from the vacuum expectation values of B − L breaking fields are also discussed.

Cosmological signals of a mirror twin Higgs

“…This is then combined with the rate of energy transferred from annihilation. A similar calculation of these rates was recently performed in [11], for cases where the Yukawa couplings do not respect the Z 2 twin symmetry.…”

“…The interaction strength is determined by the masses of the fermions through their Yukawa couplings, as well as the mixing angle of the SM-like mass state h with the gauge eigenstate h B , giving a 4-fermion coupling of strength m f mf m 2 h f 2 (here m f and mf are the masses of fermions f andf ). See [11,19] for a more detailed discussion of the cross sections. This effective interaction is appropriate for the temperatures of interest here and helps to simplify the integrals of (3.4).…”

“…Previous work attempting to construct dark matter candidates in the twin sector [11][12][13][14][15][16][17][18]) has relied upon explicit Z 2 -breaking that is not present in the mirror model. Dark matter may alternatively be -42 -…”

Cosmology in Mirror Twin Higgs and neutrino masses

“…This limit on dark radiation is often quoted as a limit on the effective additional number of neutrinos ∆N eff . A small hard breaking of the Z 2 symmetry in the Yukawa sector, as discussed in [25], offers a minimal approach to address the cosmological problems of the MTH, although here we shall follow a different route. Once the bounds on ∆N eff are satisfied, cosmological puzzles such as the origin of dark matter [26] and the generation of the baryon asymmetry [27] can be addressed.…”

Supersymmetric D-term Twin Higgs

“…3 As a result the 125 GeV Higgs mass is incompatible with a large SU(4) invariant quartic term 1 This irreducible tuning may be evaded by introducing hard Z2 breaking but explicit models of this type require total tuning of O(10) % anyway [8]. 2 Cosmological constraints on Twin Higgs models generically require non-negligible Higgs decays to mirror fermions [16]. See, however, refs.…”