Speaker
Description
Axion-like particles (ALPs) are well-motivated extensions of the Standard Model that can induce photon–ALP oscillations in the presence of external magnetic fields. For very-high-energy (VHE) gamma rays, these oscillations may leave observable signatures in the spectra of astrophysical sources, such as energy-dependent flux fluctuations or spectral hardening at TeV energies.
We present a comprehensive search for ALP-induced effects using observations of four blazars (Mrk421, Mrk501, BL Lac and 1ES 1959+650, for a total of more than 900 hours) collected over a decade (2014–2024) with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the first Large-Sized Telescope (LST-1) of the Cherenkov Telescope Array Observatory (CTAO). Their broad energy coverage and energy resolution make them particularly well suited to resolve the spectral features expected from photon–ALP oscillations.
Using a Bayesian block analysis, we identify periods of approximately steady VHE emission and construct homogeneous data subsets for the ALP search. For each source, we model photon–ALP conversions occurring within the blazar jet and in the Galactic magnetic field and compute the corresponding photon survival probability. We further develop a modular statistical framework that combines multiple datasets, sources, and instruments directly at the likelihood level, maximizing the sensitivity to a common ALP signal.
No statistically significant evidence is found for ALP-induced phenomena in the VHE emission from the analyzed blazars. We therefore derive upper limits on the ALP–photon coupling strength over the ALP mass range of 1 to 1000 neV, demonstrating the potential of joint multi-source and multi-instrument analyses to probe the ALP parameter space with current and next-generation Cherenkov telescopes.
| Primary Abstract Topic | Experiment: Axions and Wave-Like-DM |
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