Axion-like particle effects on the polarization of cosmic high-energy gamma sources

TL;DR

This paper explores how axion-like particles could significantly alter the polarization signals from gamma-ray bursts, offering a new method to detect these particles through future polarimetric observations.

Contribution

It demonstrates that photon-ALP mixing in cosmic magnetic fields can modify GRB polarization patterns, providing a novel observational signature for light ALPs.

Findings

Photon-ALP mixing can drastically change GRB polarization signals.

The effect depends on the magnetic field orientation along the line of sight.

Future high-statistics polarimetric measurements can detect ALP-induced polarization features.

Abstract

Various satellite-borne missions are being planned whose goal is to measure the polarization of a large number of gamma-ray bursts (GRBs). We show that the polarization pattern predicted by current models of GRB emission can be drastically modified by the existence of very light axion-like particles (ALPs), which are present in many extensions of the Standard Model of particle physics. Basically, the propagation of photons emitted by a GRB through cosmic magnetic fields with a domain-like structure induces photon-ALP mixing, which is expected to produce a strong modification of the original photon polarization. Because of the random orientation of the magnetic field in each domain, this effect strongly depends on the orientation of the photon line of sight. As a consequence, photon-ALP conversion considerably broadens the original polarization distribution. Searching for such a peculiar feature through future high-statistics polarimetric measurements is therefore a new opportunity to discover very light ALPs.