CMB Polarization Systematics Due to Beam Asymmetry: Impact on Inflationary Science

TL;DR

This paper develops a Fourier-space analytic framework to quantify how beam asymmetries systematically contaminate CMB polarization measurements, impacting the detection of primordial gravitational waves.

Contribution

It introduces a non-perturbative, Fourier-space formalism that generalizes previous real-space results, allowing for summation of higher-order beam asymmetry effects on CMB polarization.

Findings

Derived analytic expressions for systematic signals from beam asymmetry

Demonstrated the formalism's applicability to gravitational lensing analysis

Provided tools to assess the impact on inflationary B-mode detection

Abstract

CMB polarization provides a unique window into cosmological inflation; the amplitude of the B-mode polarization from last scattering is uniquely sensitive to the energetics of inflation. However, numerous systematic effects arising from optical imperfections can contaminate the observed B-mode power spectrum. In particular, systematic effects due to the coupling of the underlying temperature and polarization fields with elliptical or otherwise asymmetric beams yield spurious systematic signals. This paper presents a non-perturbative analytic calculation of some of these signals. We show that results previously derived in real space can be generalized, formally, by including infinitely many higher-order corrections to the leading order effects. These corrections can be summed and represented as analytic functions when a fully Fourier-space approach is adopted from the outset. The formalism and results presented in this paper were created to determine the susceptibility of CMB polarization probes of the primary gravitational wave signal but can be easily extended to the analysis of gravitational lensing of the CMB.