Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR Experiment

Abstract

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 cosmological model. This measurement demonstrates 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.

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Affiliated Institutions

• University of California, Berkeley US
• Université Paris Cité FR
• Lawrence Berkeley National Laboratory US
• Scuola Internazionale Superiore di Studi Avanzati IT
• University of Oxford GB
• University of Colorado Boulder US
• Miller College US
• Kavli Institute for the Physics and Mathematics of the Universe JP
• Sorbonne Paris Cité FR
• Napa Valley College US
• Three-Speed Logic (Canada) CA
• Laboratory for Atmospheric and Space Physics US
• Centre National de la Recherche Scientifique FR
• University of Chicago US
• Tel Aviv University IL
• Rutherford Appleton Laboratory GB
• University of California, San Diego US
• Princeton University US
• Columbia University US
• Imperial College London GB
• The Graduate University for Advanced Studies, SOKENDAI JP
• Dalhousie University CA
• High Energy Accelerator Research Organization JP
• McGill University CA
• Austin College US
• Cardiff University GB
• The University of Tokyo JP
• Laboratoire AstroParticule et Cosmologie FR
• Goddard Space Flight Center US
• The University of Osaka JP
• Commissariat à l'Énergie Atomique et aux Énergies Alternatives FR

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