CMB polarization anisotropies from cosmological reionization: extension
  to B-modes
  The accurate understanding of the ionization history of the Universe plays a
fundamental role in modern cosmology. It includes a phase of cosmological
reionization after the standard recombination epoch, possibly associated to the
early stages of structure and star formation. While the simple
"{\tau}-parametrization" of the reionization process and, in particular, of its
imprints on the CMB anisotropy likely represents a sufficiently accurate
modelling for the interpretation of current CMB data, a great attention has
been recently posed on the accurate computation of the reionization signatures
in the CMB for a large variety of astrophysical scenarios and physical
processes. This work is aimed at a careful characterization of the imprints
introduced in the polarization anisotropy, with particular attention to the
B-modes. We have implemented a modified version of CAMB, the Cosmological
Boltzmann code for computing the angular power spectrum (APS) of the
anisotropies of the CMB, to introduce the hydrogen and helium ionization
fractions predicted in astrophysical and phenomenological reionization
histories, beyond the simple {\tau}-parametrization. We compared the results
obtained for these models for all the non-vanishing (in the assumed scenarios)
modes of the CMB APS. The amplitude and shape of the B-mode APS depends, in
particular, on the tensor-to-scalar ratio, r, and on the reionization history,
thus an accurate modeling of the reionization process will have implications
for the precise determination of r or to set more precise constraints on it
through the joint analysis of E and B-mode polarization data available in the
next future and from a mission of next generation. Considering also the
limitation from potential residuals of astrophysical foregrounds, we discussed
the capability of next data to disentangle between different reionization
scenarios in a wide range of r.
