Cosmic Ray Anomalies and Dark Matter Annihilation to Muons via a Higgs
  Portal Hidden Sector
  Annihilating dark matter (DM) models based on a scalar hidden sector with
Higgs portal-like couplings to the Standard Model are considered as a possible
explanation for recently observed cosmic ray excesses. Two versions of the
model are studied, one with non-thermal DM as the origin of the boost factor
and one with Sommerfeld enhancement. In the case of non-thermal DM, four hidden
sector scalars which transform under a U(1)_{X} symmetry are added. The
heaviest scalars decouple and later decay to DM scalars, so providing the boost
factor necessary to explain the present DM annihilation rate. The mass of the
annihilating scalars is limited to < 600 GeV for the model to remain
perturbative. U(1)_{X} breaking to Z_2 at the electroweak transition mixes
light O(100) MeV hidden sector scalars with the Higgs. The DM scalars
annihilate to these light scalars, which subsequently decay to two mu^{+}
mu^{-} pairs via Higgs mixing, so generating a positron excess without
antiprotons. Decay to \mu^{+}\mu^{-} rather than e^{+}e^{-} is necessary to
ensure a fast enough light scalar decay rate to evade light scalar domination
at nucleosynthesis. In the version with Sommerfeld enhancement only three new
scalars are necessary. TeV scale DM masses can be accomodated, allowing both
the higher energy electron plus positron excess and the lower energy PAMELA
positron excess to be explained. DM annihilates to two \mu^{+}\mu^{-} pairs as
in the non-thermal model. This annihilation mode may be favoured by recent
observations of the electron plus positron excess by FERMI and HESS.
