Speaker
Mr
Aaron Vincent
(McGill University)
Description
We reconsider Sommerfeld-enhanced annihilation of dark matter (DM) into leptons to
explain PAMELA and Fermi electron and positron observations, in light of possible new
effects from substructure. There is strong tension between getting a large enough
lepton signal while respecting constraints on the fluxes of associated gamma rays. We
first show that these constraints become significantly more stringent than in
previous studies when the contributions from background e^+ e^- are taken into
account, so much so that even cored DM density profiles are ruled out. We then show
how DM annihilations within subhalos can get around these constraints. Specifically,
if most of the observed lepton excess comes from annihilations in a nearby (within 1
kpc) subhalo along a line of sight toward the galactic center, it is possible to
match both the lepton and gamma ray observations. We demonstrate that this can be
achieved in a simple class of particle physics models in which the DM annihilates via
a hidden leptophilic U(1) vector boson, with explicitly computed Sommerfeld
enhancement factors. Gamma ray constraints on the main halo annihilations (and CMB
constraints from the era of decoupling) require the annihilating component of the DM
to be subdominant, of order 10^-2 of the total DM density.
Primary author
Mr
Aaron Vincent
(McGill University)
Co-authors
Prof.
James Cline
(McGill University)
Mr
Wei Xue
(McGill University)
