Improved upper limit on degree-scale CMB B-mode polarization power from the 670 square-degree POLARBEAR survey

TL;DR

This paper presents an improved measurement of the CMB B-mode polarization power spectrum over 670 square degrees, utilizing an enhanced data analysis method to better constrain the tensor-to-scalar ratio and foreground contamination.

Contribution

The study introduces an angle-correction algorithm that increases data volume and improves the measurement of the CMB B-mode spectrum from POLARBEAR data.

Findings

Measured B-mode spectrum consistent with ΛCDM and dust foregrounds

Placed an upper limit on tensor-to-scalar ratio r < 0.33

Enhanced data analysis increased data volume by 1.8 times

Abstract

We report an improved measurement of the degree-scale cosmic microwave background $B$-mode angular-power spectrum over 670 square-degree sky area at 150 GHz with POLARBEAR. In the original analysis of the data, errors in the angle measurement of the continuously rotating half-wave plate, a polarization modulator, caused significant data loss. By introducing an angle-correction algorithm, the data volume is increased by a factor of 1.8. We report a new analysis using the larger data set. We find the measured $B$-mode spectrum is consistent with the $\Lambda$CDM model with Galactic dust foregrounds. We estimate the contamination of the foreground by cross-correlating our data and Planck 143, 217, and 353 GHz measurements, where its spectrum is modeled as a power law in angular scale and a modified blackbody in frequency. We place an upper limit on the tensor-to-scalar ratio $r$ < 0.33 at 95% confidence level after marginalizing over the foreground parameters.