Probing P- and CP-violation in dark matter interactions
  Discrete symmetries played a central role in elucidating the structure of the
weak interactions, and they will probably be equally crucial regarding the
interactions of the dark matter (DM) particle -- whose nature remains elusive.
In this work we show that signals in future direct detection experiments can be
used to test, in a model-independent way, for P- and CP-violation in DM-nucleus
interactions. The analysis is performed within the most general effective
theory for non-relativistic spin-0 DM-nucleus interactions mediated by the
exchange of a heavy particle. Assuming an idealised xenon detector, we
calculate the expected number of DM signal events required to reject P and CP
invariant DM-nucleus interactions. For a DM mass of 30 GeV (or higher), this
number lies between about 10 and 300 DM signal events, depending on how P and
CP invariance are modeled. Future direct detection experiments, therefore, have
the potential to reveal P- and CP-violation in DM interactions, making a
decisive step toward the identification of the DM particle.
