We present a measurement of the B-mode polarization power spectrum of the cosmic microwave background (CMB) using taken from July 2014 to December 2016 with the Polarbear experiment. The CMB power spectra are measured using observations at 150 GHz with an instantaneous array sensitivity of NET array = 23 µK √ s on a 670 square degree patch of sky centered at (RA, Dec)=(+0 h 12 m 0 s , −59 • 18 ). A continuously rotating half-wave plate is used to modulate polarization and to suppress low-frequency noise. We achieve 32 µK-arcmin effective polarization map noise with a knee in sensitivity of = 90, where the inflationary gravitational wave signal is expected to peak. The measured B-mode power spectrum is consistent with a ΛCDM lensing and single dust component foreground model over a range of multipoles 50 ≤ ≤ 600. The data disfavor zero C BB at 2.2σ using this range of Polarbear data alone. We cross-correlate our data with Planck full mission 143, 217, and 353 GHz frequency maps and find the low-B-mode power in the combined dataset to be consistent with thermal dust emission. We place an upper limit on the tensor-to-scalar ratio r < 0.90 at 95% confidence level after marginalizing over foregrounds.

We report a measurement of the E-mode polarization power spectrum of the cosmic microwave background (CMB) using 150 GHz data taken from July 2014 to December 2016 with the Polarbear experiment. We reach an effective polarization map noise level of 32 µK-arcmin across an observation area of 670 square degrees. We measure the EE power spectrum over the angular multipole range 500 ≤ < 3000, tracing the third to seventh acoustic peaks with high sensitivity. The statistical uncertainty on E-mode bandpowers is ∼2.3 µK 2 at ∼ 1000 with a systematic uncertainty of 0.5 µK 2. The data are consistent with the standard ΛCDM cosmological model with a probability-to-exceed of 0.38. We combine recent CMB E-mode measurements and make inferences about cosmological parameters in ΛCDM as well as in extensions to ΛCDM. Adding the ground-based CMB polarization measurements to the Planck dataset reduces the uncertainty on the Hubble constant by a factor of 1.2 to H 0 = 67.20 ± 0.57 km s −1 Mpc −1. When allowing the number of relativistic species (N eff) to vary, we find N eff = 2.94 ± 0.16, which is in good agreement with the standard value of 3.046. Instead allowing the primordial helium abundance (Y He) to vary, the data favor Y He = 0.248 ± 0.012. This is very close to the expectation of 0.2467 from Big Bang Nucleosynthesis. When varying both Y He and N eff , we find N eff = 2.70 ± 0.26 and Y He = 0.262 ± 0.015.

Using only cosmic microwave background polarization data from the POLARBEAR experiment, we measure B-mode polarization delensing on sub-degree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a mean of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments.

We present the first measurement of cross-correlation between the lensing potential, reconstructed from cosmic microwave background (CMB) polarization data, and the cosmic shear field from galaxy shapes. This measurement is made using data from the POLARBEARCMB experiment and the Subaru Hyper Suprime-Cam (HSC) survey. By analyzing an 11 deg 2 overlapping region, we reject the null hypothesis at 3.5σand constrain the amplitude of the cross-spectrum to =  A 1.70 0.48 lens  , where A lens  is the amplitude normalized with respect to the Planck2018 prediction, based on the flat Λ cold dark matter cosmology. The first measurement of this crossspectrum without relying on CMB temperature measurements is possible owing to the deep POLARBEAR map with a noise level of ∼6 μK arcmin, as well as the deep HSC data with a high galaxy number density of = n 23 arcmin g 2. We present a detailed study of the systematics budget to show that residual systematics in our results are negligibly small, which demonstrates the future potential of this cross-correlation technique.