Irregularity in gamma ray source spectra as a signature of axionlike particles

Understand

Oscillations from high energy photons into light pseudoscalar particles in an external magnetic field are expected to occur in some extensions of the standard model.

• It is usually assumed that those axionlike particles (ALPs) could produce a drop in the energy spectra of gamma ray sources and possibly decrease the opacity of the Universe for TeV gamma rays.
• We show here that these assumptions are in fact based on an average behavior that cannot happen in real observations of single sources.
• We propose a new method to search for photon-ALP oscillations, taking advantage of the fact that a single observation would deviate from the average expectation.