Polarization analysis of gravitational-wave backgrounds from the correlation signals of ground-based interferometers: measuring a circular-polarization mode

TL;DR

This paper explores how ground-based gravitational-wave detectors can measure the circular polarization of backgrounds, providing a potential probe for parity violation in the universe by analyzing the Stokes V parameter.

Contribution

It introduces a theoretical framework for measuring circular polarization in gravitational-wave backgrounds using detector networks, extending beyond traditional total amplitude analysis.

Findings

Separation of polarized and unpolarized modes is feasible with next-generation detectors.

Inclusion of circular polarization analysis enhances understanding of gravitational-wave backgrounds.

The method maintains small statistical loss despite mode correlation.

Abstract

The Stokes V parameter characterizes asymmetry of amplitudes between right- and left-handed waves, and non-vanishing value of the V parameter yields a circularly polarized signal. Cosmologically, V parameter may be a direct probe for parity violation in the universe. In this paper, we theoretically investigate a measurement of this parameter, particularly focusing on the gravitational-wave backgrounds observed via ground-based interferometers. In contrast to the traditional analysis that only considers the total amplitude (or equivalently $\Omega_{GW}$), the signal analysis including a circular-polarized mode has a rich structure due to the multi-dimensionality of target parameters. We show that, by using the network of next-generation detectors, separation between polarized and unpolarized modes can be performed with small statistical loss induced by their correlation.