Determination of Polarization Angles in CMB Experiments and Application
  to CMB Component Separation Analyses
  The new generation of CMB polarization experiments will reach limits of
sensitivity never achieved before to detect the primordial B-mode signal.
However, all these efforts will be futile if we lack a tight control of
systematics. Here, we focus on the systematic that arises from the uncertainty
on the calibration of polarization angles. Miscalibrated polarization angles
induce a mixing of E- and B-modes that obscures the primordial B-mode signal.
We introduce an iterative angular power spectra maximum likelihood-based method
to calculate polarization angles from the multi-frequency signal. The basis
behind this methodology grounds on nulling the EB power spectra. To simplify
the likelihood, we assume that the rotation angles are small (<6 deg) and, the
maximum likelihood solution for the rotation angles is obtained by applying an
iterative process where the covariance matrix does not depend on the angles per
iteration, i.e., the rotation angles are fixed to the estimated angles in the
previous iteration. With these assumptions, we obtain an analytical linear
system which leads to a very fast computational implementation. We show that
with this methodology we are able to determine the rotation angle for each
frequency with sufficiently good accuracy. To prove the latter point we perform
component separation analyses using the parametric component separation method
B-SeCRET with two different approaches. In the first approach we apply the
B-SeCRET pipeline to the signal de-rotated with the estimation of the angles,
while in the second, the rotation angles are treated as model parameters using
the estimation of the angles as a prior information. We obtain that the
rotation angles estimations improve after applying the second approach, and
show that the systematic residuals due to the non-null calibration polarization
angles are mitigated to the order of a 1% at the power spectrum level.
