Speaker
Jure Zupan
Description
We consider the hypothesis that Dark Matter (DM) has tree-level
interactions only with leptons. Such a framework, where DM recoils
against electrons bound in atoms, has been proposed as an explanation
for the annually modulated scintillation signal in DAMA/LIBRA versus
the absence of a signal for nuclear recoils in experiments like CDMS or
XENON10. However, even in such a leptophilic DM scenario there are
loop induced DM-hadron interactions, where the photons emitted from virtual
leptons couple to the charge of a nucleus. Using a general effective
field theory approach we show that, if such an interaction is induced at
one or two-loop level, then DM-nucleus scattering dominates over
DM-electron scattering. This is because the latter is suppressed by
the bound state wave function. One obtains a situation similar to standard
DM-nucleus scattering analyses with considerable tension between the
results of DAMA and CDMS/XENON10. This conclusion does not apply in
the case of pseudoscalar or axial vector coupling between DM and leptons,
where the loop diagrams vanish. In this case the explanation of the
DAMA signal in terms of DM-electron scattering is strongly disfavored by
the spectral shape of the signal. Furthermore, if DM can annihilate into
neutrinos or tau leptons, the required cross sections are excluded by
many orders of magnitude using the Super-Kamiokande bound on neutrinos
from DM annihilations in the Sun.
