A note on the birefringence angle estimation in CMB data analysis

TL;DR

This paper examines methods to estimate cosmological birefringence angle in CMB data, analyzing the properties of D-estimators and their interaction with weak-lensing effects, to improve constraints on parity-violating physics.

Contribution

It provides a detailed framework for both frequentist and Bayesian analysis of birefringence angle estimation using CMB polarization data, including the effects of weak-lensing.

Findings

Analysis of D-estimators for birefringence angle

Framework for combined frequentist and Bayesian methods

Discussion of weak-lensing impact on polarization correlations

Abstract

Parity violating physics beyond the standard model of particle physics induces a rotation of the linear polarization of photons. This effect, also known as cosmological birefringence (CB), can be tested with the observations of the cosmic microwave background (CMB) anisotropies which are linearly polarized at the level of $5-10\%$. In particular CB produces non-null CMB cross correlations between temperature and B mode-polarization, and between E- and B-mode polarization. Here we study the properties of the so called D-estimators, often used to constrain such an effect. After deriving the framework of both frequentist and Bayesian analysis, we discuss the interplay between birefringence and weak-lensing, which, albeit parity conserving, modifies pre-existing TB and EB cross correlation.