SUSY Implications from WIMP Annihilation into Scalars at the Galactic
  Centre
  An excess in gamma-rays emanating from the galactic centre has recently been
observed in the Fermi-LAT data. This signal can be interpreted as resulting
from WIMP annihilation, with the spectrum well-fit by dark matter annihilating
dominantly into either bottom-quark or Higgs pairs. Supersymmetric models
provide a well-motivated framework to study the implications of this signal in
these channels. With a neutralino dark matter candidate, the gamma-ray excess
cannot be easily accommodated in the minimal supersymmetric model, which in any
case requires tuning below the percent level to explain the observed Higgs
mass. Instead we are naturally led to consider the next-to-minimal model with a
singlet superfield. This not only allows for the annihilation channel into
bottom-quark pairs to be implemented, but also provides new possibilities for
annihilation into Higgs-pseudoscalar pairs. We show that the fit to the
gamma-ray excess for the Higgs-pseudoscalar channel can be just as good as for
annihilation into bottom-quark pairs. Moreover, in the parameter range of
interest, the next-to-minimal supersymmetric model solves the mu-problem and
can explain the 125 GeV Higgs mass with improved naturalness. We also consider
an extension by adding a right-handed neutrino superfield with the right-handed
sneutrino acting as a dark matter candidate. Interestingly, this allows for the
annihilation into pseudoscalar pairs which also provide a good fit to the
gamma-ray excess. Furthermore, in the case of a neutralino LSP, the late decay
of a sneutrino NLSP can non-thermally produce the observed relic abundance.
Finally, the WIMP annihilation into scalar pairs allows for the possibility of
detecting the Higgs or pseudoscalar decay into two photons, providing a
smoking-gun signal of the model.
