John Kearney, Aaron Pierce
We revisit the annihilation of dark matter to neutrinos in the Sun near the
WW and tt kinematic thresholds. We investigate the potential importance of
annihilation to WW* in a minimal dark matter model in which a Majorana singlet
is mixed with a vector-like electroweak doublet, but many results generalize to
other models of weakly-interacting dark matter. We re-evaluate the indirect
detection constraints on this model and find that, once all annihilation
channels are properly taken into account, the most stringent constraints on
spin-dependent scattering for dark matter mass 60 GeV < mX < mt are derived
from the results of the Super-Kamiokande experiment. Moreover, we establish the
model-independent statement that Majorana dark matter whose thermal relic
abundance and neutrino signals are both controlled by annihilation via an
s-channel Z boson is excluded for 70 GeV < mX < mW. In some models,
annihilation to tt* can affect indirect detection, notably by competing with
annihilation to gauge boson final states and thereby weakening neutrino
signals. However, in the minimal model, this final state is largely negligible,
only allowing dark matter with mass a few GeV below the top quark mass to evade
exclusion.
View original:
http://arxiv.org/abs/1202.0284
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