Two-point Correlation Function of WMAP 9 year data
  Using an optimal estimator for the CMB Angular Power Spectrum we compute the
temperature two-point correlation function of WMAP 9 year at low resolution.
Supported by realistic Monte-Carlo simulations, we evaluate how such observed
function depends on the Galactic mask. We find that it is more and more
consistent with zero (i.e. no correlation) as the Galactic mask is increased.
In particular we estimate that such a behavior happens very rarely in a
$\Lambda$CDM model, i.e. $<0.01%$ of the realizations when we adopt a mask
which leaves 46% of observed sky. This is evaluated for the so called $S_{1/2}$
estimator, already well known in literature \citep{Spergel:2003cb}. Also for
its generalization to the whole angular range $[0, \pi]$, namely $S_{1}$, we
find a very unlikely behavior which is $ \lesssim 0.04%$ C.L. for the
considered masks that cover at least $\sim 54%$ of the sky.
