Composite magnetic dark matter and the 130 GeV line
  We propose an economical model to explain the apparent 130 GeV gamma ray
peak, found in the Fermi/LAT data, in terms of dark matter annihilation through
a dipole moment interaction. The annihilating dark matter particles represent a
subdominant component, with mass density 7-17% of the total DM density; and
they only annihilate into gamma gamma, gamma Z, and ZZ, through a magnetic (or
electric) dipole moment. Annihilation into other standard model particles is
suppressed, due to a mass splitting in the magnetic dipole case, or to p-wave
scattering in the electric dipole case. In either case, the observed signal
requires a dipole moment of strength mu ~ 2/TeV. We argue that composite models
are the preferred means of generating such a large dipole moment, and that the
magnetic case is more natural than the electric one. We present a simple model
involving a scalar and fermionic techniquark of a confining SU(2) gauge
symmetry. We point out some generic challenges for getting such a model to
work. The new physics leading to a sufficiently large dipole moment is below
the TeV scale, indicating that the magnetic moment is not a valid effective
operator for LHC physics, and that production of the strongly interacting
constituents, followed by techni-hadronization, is a more likely signature than
monophoton events. In particular, 4-photon events from the decays of bound
state pairs are predicted.
