MiXDM: Cosmic Ray Signals from Multiple States of Dark Matter
  Recent data from cosmic ray experiments such as PAMELA, Fermi, ATIC and
PPB-BETS all suggest the need for a new primary source of electrons and
positrons at high (>~100 GeV) energies. Many proposals have been put forth to
explain these data, usually relying on a single particle to annihilate or decay
to produce e+e-. In this paper, we consider models with multiple species of
WIMPs with significantly different masses. We show if such dark matter
candidates chi_i annihilate into light bosons, they naturally produce equal
annihilation rates, even as the available numbers of pairs for annihilation
n_chi_i^2 differ by orders of magnitude. We argue that a consequence of these
models can be to add additional signal naturally at lower (~100 GeV) versus
higher (~ TeV) energies, changing the expected spectrum and even adding bumps
at lower energies, which may alleviate some of the tension in the required
annihilation rates between PAMELA and Fermi. These spectral changes may yield
observable consequences in the microwave Haze signal observed at the upcoming
Planck satellite. Such a model can connect to other observable signals such as
DAMA and INTEGRAL by having the lighter (heavier) state be a pseudo-Dirac
fermion with splitting 100 keV (1 MeV). We show that variations in the halo
velocity dispersion can alleviate constraints from final state radiation in the
galactic center and galactic ridge. If the lighter WIMP has a large
self-interaction cross section, the light-WIMP halo might collapse,
dramatically altering expectations for direct and indirect detection
signatures.
