The High Energy Physics Group is mainly involved in Astroparticle Physics , a discipline where where Particle Physics and Astrophysics join their efforts to open up a new observation window in Astronomy.
Photons imply that the electromagnetic spectrum stretches in several orders of magnitude.
Theorists sharpen their wits to accelerate photons to the Very High Energy domain. A number of ingenious models have been contrived based on pulsars or jets in active galactic nuclei. Beyond this energy, the origin is fraught with uncertainty.