Probing dark matter particles at CEPC
  We investigate the capability of the future electron collider CEPC in probing
the parameter space of several dark matter models, including millicharged dark
matter models, $Z'$ portal dark matter models, and effective field theory dark
matter models. In our analysis, the monophoton final state is used as the
primary channel to detect dark matter models at CEPC. To maximize the signal to
background significance, we study the energy and angular distributions of the
monophoton channel arising from dark matter models and from the standard model
to design a set of detector cuts. For the $Z'$ portal dark matter, we also
analyze the $Z'$ boson visible decay channel which is found to be complementary
to the monophoton channel in certain parameter space. The CEPC reach in the
parameter space of dark matter models is also put in comparison with Xenon1T.
We find that CEPC has the unprecedented sensitivity to certain parameter space
for the dark matter models considered; for example, CEPC can improve the limits
on millicharge by one order of magnitude than previous collider experiments for
${\cal O}(1)-100$ GeV dark matter.
