Dark matter in the Sun: scattering off electrons vs nucleons
  The annihilation of dark matter (DM) particles accumulated in the Sun could
produce a flux of neutrinos, which is potentially detectable with neutrino
detectors/telescopes and the DM elastic scattering cross section can be
constrained. Although the process of DM capture in astrophysical objects like
the Sun is commonly assumed to be due to interactions only with nucleons, there
are scenarios in which tree-level DM couplings to quarks are absent, and even
if loop-induced interactions with nucleons are allowed, scatterings off
electrons could be the dominant capture mechanism. We consider this possibility
and study in detail all the ingredients necessary to compute the neutrino
production rates from DM annihilations in the Sun (capture, annihilation and
evaporation rates) for velocity-independent and isotropic, velocity-dependent
and isotropic and momentum-dependent scattering cross sections for DM
interactions with electrons and compare them with the results obtained for the
case of interactions with nucleons. Moreover, we improve the usual calculations
in a number of ways and provide analytical expressions in three appendices.
Interestingly, we find that the evaporation mass in the case of interactions
with electrons could be below the GeV range, depending on the high-velocity
tail of the DM distribution in the Sun, which would open a new mass window for
searching for this type of scenarios.
