Photon-neutrino scattering and the B-mode spectrum of CMB photons
  On the basis of the quantum Boltzmann equation governing the time-evolution
of the density matrix of polarized CMB photons in the primordial scalar
perturbations of metric, we calculate the B-mode spectrum of polarized CMB
photons contributed from the scattering of CMB photons and CNB neutrinos
(Cosmic Neutrino Background). We show that such contribution to the B-mode
spectrum is negligible for small $\ell$, however is significantly large for $50
< \ell< 200$ by plotting our results together with the BICEP2 data. Our study
and results imply that in order to theoretically better understand the origin
of the observed B-mode spectrum of polarized CMB photons ($r$-parameter), it
should be necessary to study the relevant and dominate processes in both tensor
and scalar perturbations.
