Special Astronomy & Astrophysics Seminar: Extragalactic cosmic-ray phenomenology

Abstract:

In the past few years, new measurements (brought by experiments such as Kascade-Grande, the Pierre Auger Observatory or Telescope Array) have radically improved our knowledge of the highest energy domain of the cosmic-ray spectrum. In particular (and surprisingly for most of the scientists involved in the field) the Auger composition analyses strongly favors a composition getting gradually heavier above a few 10^18 eV.

In this talk, I will discuss the phenomenology of extragalactic cosmic-ray propagation. The critical importance of the ultra-high-energy (UHE) source composition on the spectrum and composition expected on Earth as well as on the phenomenology of the transition between Galactic and extragalactic cosmic-rays will be reviewed. We will see that the evolution of the UHE cosmic-ray composition deduced from Auger data can be understood with fairly simple models (assuming standard candle sources) but that the global understanding of the cosmic-ray spectrum and composition on a wide energy range probably requires to build more elaborated models. I will finally discuss multimessenger constrains brought by neutrino and gamma-ray experiments.

Seminar Organizer: Prof. Sara Beck