Constraints on cosmological birefringence from Planck and Bicep2/Keck data

TL;DR

This paper uses Planck and Bicep2/Keck data to constrain cosmological birefringence, finding no significant rotation of CMB polarization and forecasting future improvements with additional spectra.

Contribution

It provides new constraints on the birefringence angle using recent polarization data and forecasts future sensitivity improvements with high-ell spectra inclusion.

Findings

Constraints on birefringence angle are consistent with zero.

Planck data yields $ heta = 0.0^ ext{o} \, ext{±} \, 1.3^ ext{o}$ (stat+sys).

Bicep2/Keck data yields $ heta = 0.30^ ext{o} \, ext{±} \, 0.27^ ext{o}$ (stat) with systematic uncertainty.

Abstract

The polarization of cosmic microwave background (CMB) can be used to constrain cosmological birefringence, the rotation of the linear polarization of CMB photons potentially induced by parity violating physics beyond the standard model. This effect produces non-null CMB cross correlations between temperature and B mode-polarization, and between E- and B-mode polarization. Both cross-correlations are otherwise null in the standard cosmological model. We use the recently released 2015 Planck likelihood in combination with the Bicep2/Keck/Planck (BKP) likelihood to constrain the birefringence angle $\alpha$. Our findings, that are compatible with no detection, read $\alpha = 0.0^{\circ} \pm 1.3^{\circ} \mbox{ (stat)} \pm 1^{\circ} \mbox{ (sys)} $ for {\sc Planck} data and $\alpha = 0.30^{\circ} \pm 0.27^{\circ} \mbox{ (stat)} \pm 1^{\circ} \mbox{(sys)} $ for BKP data. We finally forecast the expected improvements over present constraints when the Planck BB, TB and EB spectra at high $\ell$ will be included in the analysis.