  We present a comprehensive analysis of the loop induced top quark FCNC
signals at the LHC within one class of the simplified model. The loop level
FCNC interactions are well motivated to avoid the hierarchy of the top quark
couplings from the new physics and standard model. Such a theory will posit a
Majorana dark matter candidate and could be tested through dark matter relic
density, direct detection experiments (the scattering between dark matter and
heavy nuclei), and the collider signals at the LHC. We find that the
spin-independent (SI) scattering between Majorana dark matter and nuclei will
vanish at the leading order, while the next-to-leading order correction to the
SI scattering becomes significance to constrain the parameter space of the
model. A detailed comparison from direct detection experiments and LHC searches
is also discussed and both of them are very important to full constrain the
model.
