Search for Axion-like Particles Using TeV Blazar Observations with the HAWC Observatory

Axion-like particles (ALPs) are hypothetical pseudoscalar particles predicted in several extensions of the Standard Model. These particles have the potential to address both the dark matter problem and the strong CP problem. One method to detect ALPs is through the phenomenon of ALP-photon oscillation in the presence of magnetic fields. In high-energy astrophysics, ALP-photon oscillation can manifest as an increased transparency of TeV gamma rays from extragalactic sources. In this work, we present a search for ALPs using gamma-ray observations of VER J0521+211, obtained with the High-Altitude Water Cherenkov (HAWC) Observatory. For the blazar, we calculate the photon survival probabilities across different regions of the ALP parameter space, assuming both the presence and absence of ALPs. By fitting the expected spectra of these two scenarios and comparing the resulting likelihoods, we establish upper limits on the parameters of ALPs. We present new constraints on the coupling strength between ALPs and photons for ALP masses in the neV range.