Inert Doublet Dark Matter with Strong Electroweak Phase Transition

Abstract

We reconsider the strength of the electroweak phase transition (EWPT) in the inert doublet dark matter model, using a quantitatively accurate form for the one-loop finite temperature effective potential, taking into account relevant particle physics and dark matter constraints, focusing on a standard model Higgs mass near 126 GeV, and doing a full scan of the space of otherwise unconstrained couplings. We find that there is a significant (although fine-tuned) space of parameters for achieving an EWPT sufficiently strong for baryogenesis while satisfying the Xenon100 constraints from direct detection and not exceeding the correct thermal relic density. We predict that the dark matter mass should be in the range 60-67 GeV, and we discuss possible LHC signatures of the charged and CP-odd Higgs bosons, including a 10% decrease of the h -> 2 photon branching ratio.

6 pages, 4 figures. v2: added discussion of subdominant IDM DM, and references; v4: improved fig. 1, added discussion of uncertainty in Higgs-nucleon coupling; published version; v5: fixed typo in eq. (5); v6: corrected fig. 2 to account for thermal averaging of cross section near resonance; v7: corrected sign of contribution to Higgs to two photon partial width