Search for ultra-light axions with CMB polarization

TL;DR

This paper investigates the potential of using CMB polarization measurements to detect ultra-light axion-like particles through their predicted cosmic birefringence effect, which could reveal new physics beyond the Standard Model.

Contribution

It analyzes how current and future CMB polarization data can constrain the properties of ultra-light axions, focusing on their coupling and mass parameters.

Findings

Recent measurements suggest a possible isotropic birefringence angle of about 0.3 degrees.

CMB data could constrain axion masses below 10^{-27} eV and coupling constants above 10^{-20} GeV^{-1}.

Confirmation of birefringence would imply new physics related to axion-like particles.

Abstract

When coupled to electromagnetism via a Chern-Simons interaction, axion-like particles (ALP) produce a rotation of the plane of linear polarization of photons known as cosmic birefringence. Recent measurements of cosmic birefringence obtained from the polarization of the cosmic microwave background (CMB) hint at the existence of an isotropic birefringence angle of $\beta\approx 0.3^\circ$, currently excluding $\beta=0$ with a statistical significance of $3.6\sigma$. Were such measurement to be confirmed as a cosmological signal, CMB information alone could constrain the ALP parameter space for masses $m_\phi\lesssim 10^{-27}$eV and axion-photon coupling constants $g_{\phi\gamma}\gtrsim 10^{-20}$GeV$^{-1}$.