A measurement of the cosmic microwave background B mode polarization power spectrum at subdegree scales from two years of Polarbear data

Abstract

We report an improved measurement of the cosmic microwave background B-mode polarization power spectrum with the POLARBEAR. experiment at 150 GHz. By adding new data collected during the second season of observations (2013-2014) to re-analyzed data from the first season (2012-2013), we have reduced twofold the band-power uncertainties. The band powers are reported over angular multipoles 500 <= l <= 2100, where the dominant B-mode signal is expected to be due to the gravitational lensing of E-modes. We reject the null hypothesis of no B-mode polarization at a confidence of 3.1 sigma including both statistical and systematic uncertainties. We test the consistency of the measured B-modes with the. Cold Dark Matter (Lambda CDM) framework by fitting for a single lensing amplitude parameter A(L) relative to the Planck. 2015 best-fit model prediction. We obtain A(L) = 0.60(-0.24)(+0.26)(stat)(-0.04)(+0.00)(inst) +/- 0.14(foreground) +/- 0.04(multi), where A(L) = 1 is the fiducial Lambda CDM value.