Dark Matter, Dark Radiation and Gravitational Waves from Mirror Higgs Parity

Abstract

An exact parity replicates the Standard Model giving a Mirror Standard Model, SM $\leftrightarrow$ SM${}^{\prime }$. This "Higgs Parity" and the mirror electroweak symmetry are spontaneously broken by the mirror Higgs, $⟨H^{\prime }⟩=v^{\prime }\gg ⟨H⟩$, yielding the Standard Model Higgs as a Pseudo-Nambu-Goldstone Boson of an approximate $SU(4)$ symmetry, with a quartic coupling $\hat{I}{»}_{SM}(v^{\prime })\sim 10^{-3}$. Mirror electromagnetism is unbroken and dark matter is composed of $e^{\prime }$ and ${\bar{e}}^{\prime }$. Direct detection may be possible via the kinetic mixing portal, and in unified theories this rate is correlated with the proton decay rate. With a high reheat temperature after inflation, the $e^{\prime }$ dark matter abundance is determined by freeze-out followed by dilution from decays of mirror neutrinos, $\hat{I}{½}^{\prime }\to \ell H$. Remarkably, this requires $v^{\prime }\sim (10^8-10^{10})$ GeV, consistent with the Higgs mass, and a Standard Model neutrino mass of $(10^{-2}-10^{-1})$ eV, consistent with observed neutrino masses. The mirror QCD sector exhibits a first order phase transition producing gravitational waves that may be detected by future observations. Mirror glueballs decay to mirror photons giving dark radiation with $\hat{I}”N_{\mathrm{eff}}\sim 0.03-0.4$. With a low reheat temperature after inflation, the $e^{\prime }$ dark matter abundance is determined by freeze-in from the SM sector by either the Higgs or kinetic mixing portal.

40 pages, 15 figures