Constraints on axion-like particles from the observation of Galactic sources by the LHAASO

High-energy photons may oscillate with axion-like particles（ALPs） when they propagate through the Milky Way's magnetic field,resulting in an alteration in the observed photon energy spectrum.Ultra-high energy gamma-ray spectra,measured by the Large High Altitude Air Shower Observatory（LHAASO） up to O（1） PeV,provide a promising opportunity to investigate the ALP-photon oscillation effect.In this study,we utilize the gamma-ray spectra of four Galactic sources measured by the LHAASO,that is,the Crab Nebula,LHAASO J2226+6057,LHAASO J1908+0621,and LHAASO J1825-1326,to explore this effect.We employ the CLs method to set constraints on the ALP parameters.Our analysis of the observations of the four sources reveals that the ALPphoton coupling gaγ is constrained to be smaller than 1.4×10-10 GeV-1 for an ALP mass of ～4×10-7 eV at 95%C.L.Combining the observations of the Crab Nebula from the LHAASO and other experiments,we find that the ALP-photon coupling may be set to approximately 7.5×10-11 GeV-1 for an ALP mass of ～4×10-7 eV,which is similar to the CAST constraint.