Chasing a consistent picture for dark matter direct searches
  In this paper we assess the present status of dark matter direct searches by
means of Bayesian statistics. We consider three particle physics models for
spin-independent dark matter interaction with nuclei: elastic, inelastic and
isospin violating scattering. We shortly present the state of the art for the
three models, marginalising over experimental systematics and astrophysical
uncertainties. Whatever the scenario is, XENON100 appears to challenge the
detection region of DAMA, CoGeNT and CRESST. The first aim of this study is to
rigorously quantify the significance of the inconsistency between XENON100 data
and the combined set of detection (DAMA, CoGeNT and CRESST together),
performing two statistical tests based on the Bayesian evidence. We show that
XENON100 and the combined set are inconsistent at least at 2 sigma level in all
scenarios but inelastic scattering, for which the disagreement drops to 1 sigma
level. Secondly we consider only the combined set and hunt the best particle
physics model that accounts for the events, using Bayesian model comparison.
The outcome between elastic and isospin violating scattering is inconclusive,
with the odds 2:1, while inelastic scattering is disfavoured with the odds of
1:32 because of CoGeNT data. Our results are robust under reasonable prior
assumptions. We conclude that the simple elastic scattering remains the best
model to explain the detection regions, since the data do not support extra
free parameters. Present direct searches therefore are not able to constrain
the particle physics interaction of the dark matter. The outcome of consistency
tests implies that either a better understanding of astrophysical and
experimental uncertainties is needed, either the dark matter theoretical model
is at odds with the data.
