The Annulus-Filtered E and B Modes in CMBR Polarization

This work shows that the CMB polarization E and B modes can be measured in a clean manner in the real space by adopting a specific observing strategy: the detectors are configured to lie around a ring to observe an annulus of sky, where the antenna axis in each detector is oriented in the local radial direction. In particular, for the measurement of the weak B mode, the detector ring can be put in rotation about its axis. This additional degree of freedom allows each detector to directly measure the B-mode signal through long-term exposure to the sky without further data manipulation for removal of the E mode. We present the variances of the expected measured E andB-mode surface-brightness fluctuations as functions of the radius of the sky annulus. Both E and B modes have distinct features that can serve as the indicators for claiming detection. The temperature anisotropy-E mode correlation can also be constructed by the present method, though it is probably not optimized. Subject headings: cosmology; microwave background — polarization