Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial Cosmic Microwave Background (CMB) and thereby induces new, small-scale B -mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even-and odd-parity E -and B -mode polarization mapped over ∼ 30 square degrees of the sky measured by the Polarbear experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B -modes is found at 4.2σ (stat.+sys.) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda Cold Dark Matter (ΛCDM) cosmological model. This measurement demonstrates 2 a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B -mode signal in searches for primordial gravitational waves.Introduction: As Cosmic Microwave Background (CMB) photons traverse the Universe, their paths are gravitationally deflected by large-scale structures. By measuring the resulting changes in the statistical properties of the CMB anisotropies, maps of this gravitational lensing deflection, which traces large-scale structure, can be reconstructed. Gravitational lensing of the CMB has been detected in the CMB temperature anisotropy in several ways: in the smoothing of the acoustic peaks of the temperature power spectrum [1-3], in cross-correlations with tracers of the large-scale matter distribution [4][5][6][7][8][9][10], and in the four-point correlation function of CMB temperature maps [11][12][13][14].The South Pole Telescope (SPT) collaboration recently reported a detection of lensed polarization using the cross-correlation between maps of CMB polarization and sub-mm maps of galaxies from Herschel/SPIRE [15]. A companion paper to this one has also shown the evidence of the CMB lensing-Cosmic Infrared Background crosscorrelation results using Polarbear data [16], finding good agreement with the SPT measurements. This crosscorrelation is immune to several instrumental systematic effects but the cosmological interpretation of this measurement requires assumptions about the relation of submm galaxies to the underlying mass distribution [17].In this Letter, we present the first direct evidence for gravitational lensing of the polarized CMB using data from the Polarbear experiment. We present power spectra of the lensing deflection field for two four-point estimators using only CMB polarization data, and tests for spurious systematic contamination of these estimators. We combine the two estimators to increase the signal-to-noise of the lensing detection.CMB lens...

We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the Polarbear experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < < 2100 and is based on observations of an effective sky area of 25 deg 2 with 3. 5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A BB to the measured band powers, A BB = 1.12 ± 0.61(stat) +0.04 −0.12 (sys) ± 0.07(multi), where A BB = 1 is the fiducial wmap-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude A BB .

We present the design and characterization of the polarbear experiment. polarbear will measure the polarization of the cosmic microwave background (CMB) on angular scales ranging from the experiment's 3.5 beam size to several degrees. The experiment utilizes a unique focal plane of 1,274 antenna-coupled, polarization sensitive TES bolometers cooled to 250 milliKelvin. Employing this focal plane along with stringent control over systematic errors, polarbear has the sensitivity to detect the expected small scale B-mode signal due to gravitational lensing and search for the large scale B-mode signal from inflationary gravitational waves.polarbear was assembled for an engineering run in the Inyo Mountains of California in 2010 and was deployed in late 2011 to the Atacama Desert in Chile. An overview of the instrument is presented along with characterization results from observations in Chile.

We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.

The Polarbear Cosmic Microwave Background (CMB) polarization experiment is currently observing from the Atacama Desert in Northern Chile. It will characterize the expected B-mode polarization due to gravitational lensing of the CMB, and search for the possible B-mode signature of inflationary gravitational waves. Its 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter. Each detector's planar antenna structure is coupled to the telescope's optical system through a contacting dielectric lenslet, an architecture unique in current CMB experiments. We present the initial characterization of this focal plane.