Constraints on axionlike particles from a combined analysis of three flaring $\textit{Fermi}$ flat-spectrum radio quasars

TL;DR

This study combines gamma-ray data from three bright blazars to search for axionlike particles, accounting for jet physics and magnetic field uncertainties, ultimately setting new constraints on ALP properties.

Contribution

First combined analysis of multiple blazar observations including detailed jet physics and magnetic field uncertainties to constrain ALP parameters.

Findings

No evidence for ALPs was found.

Excluded ALP mass below 200 neV and coupling above 5×10^{-12} GeV^{-1} at 95% confidence.

Enhanced constraints compared to previous single-source analyses.

Abstract

Many theories beyond the Standard Model of particle physics predict the existence of axionlike particles (ALPs) that mix with photons in the presence of a magnetic field. Searching for the effects of ALP-photon mixing in gamma-ray observations of blazars has provided some of the strongest constraints on ALP parameter space so far. Previously, only individual sources have been analysed. We perform a combined analysis on $\textit{Fermi}$ Large Area Telescope data of three bright, flaring flat-spectrum radio quasars, with the blazar jets themselves as the dominant mixing region. For the first time, we include a full treatment of photon-photon dispersion within the jet, and account for the uncertainty in our B-field model by leaving the field strength free in the fitting. Overall, we find no evidence for ALPs, but are able to exclude the ALP parameters $m_a\lesssim200$ neV and $g_{a\gamma}\gtrsim 5 \times 10^{-12}$ GeV$^{-1}$ with 95\% confidence.