Joint constraint on primordial gravitational waves and polarization rotation angle with current CMB polarization data

Abstract

Cosmological CPT violation will rotate the polarized direction of CMB photons, convert partial CMB E mode into B mode and vice versa. It will generate non-zero EB, TB spectra and change the EE, BB, TE spectra. This phenomenon gives us a way to detect the CPT-violation signature from CMB observations, and also provides a new mechanism to produce B mode polarization. In this paper, we perform a global analysis on tensor-to-scalar ratio $r$ and polarization rotation angles based on current CMB datasets with both low $\ell$ (Planck, BICEP2/Keck Array) and high $\ell$ (POLARBEAR, SPTpol, ACTPol). Benefited from the high precision of CMB data, we obtain the isotropic rotation angle $\bar{\alpha }=-0.01^{\circ }\pm 0.37^{\circ }$ at 68% C.L., the variance of the anisotropic rotation angles $C^{\alpha }(0)<0.0032{\mathrm{rad}}^2$, the scale invariant power spectrum $D_{\ell \in [2,350]}^{\alpha \alpha }<4.71\times 10^{-5}{\mathrm{rad}}^2$ and $r<0.057$ at 95% C.L.. Our result shows that with the polarization rotation effect, the 95% upper limit on $r$ gets tightened by 17%.

Comments: 8 pages, 2 figures