Kavli Affiliate: Gordan Krnjaic
| First 5 Authors: Asher Berlin, Joshua W. Foster, Dan Hooper, Gordan Krnjaic,
| Summary:
We present a mechanism that allows thermal relic dark matter to annihilate
efficiently in the Galactic Halo and in galaxy clusters, but not in the
lower-velocity environments of dwarf spheroidal (dSph) galaxies. We realize
this within a complete model in which the dark matter consists of two distinct
states separated by a small mass splitting. An indirect detection signal is
generated only through the coannihilations of these two states, requiring both
to be present. In the halo of the Milky Way, the dark matter particles in the
lighter state can be excited into the long-lived heavier state through
scattering. Once excited, these heavier particles can coannihilate with those
in the lighter state, yielding a gamma-ray signal with little or no
suppression. By contrast, the dark matter particles in dwarf galaxies do not
possess enough kinetic energy to be excited, thereby suppressing the
coannihilation rate and corresponding indirect detection signals from those
systems. This framework breaks the predictive relationship that ordinarily
exists between these respective gamma-ray signals and complicates our ability
to interpret the results of indirect detection searches.
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