Lensing effect on polarization in the microwave background: Extracting theconvergence power spectrum - art. no. 043517

Matter inhomogeneities along the line of sight deflect the cosmic microwave background (CMB) photons originating at the last scattering surface at a r edshift z similar to 1100. These distortions modify the pattern of CMB pola rization. We identify specific combinations of Stokes Q and U parameters th at correspond to spin 0, +/-2 variables and can be used to reconstruct the projected matter density. We compute the expected signal-to-noise ratio as a function of detector sensitivity and angular resolution. With the Planck satellite the detection would be at a few sigma level. Several times better detector sensitivity would be needed to measure the projected dark matter power spectrum over a wider range of scales, which could provide an indepen dent confirmation of the projected matter power spectrum as measured from o ther methods.