Περίληψη |
Observations of extensive air showers (EAS) initiated by Ultra High Energy Cosmic Rays (UHECR), when interpreted in the conventional way, indicate a transition to heavy primaries at energies > 1018.3 eV. However, at energies > 1018.9 eV, the arrival directions of UHECRs display a dipole anisotropy. This, along with new studies showing that the Galactic magnetic field is stronger than previously believed, disfavor heavy composition, as heavy nuclei are strongly deflected by magnetic fields and thus would lose any traces of anisotropy. One solution to this problem could be the appearance of new effects beyond the Standard Model in particle interactions at center-of-mass (CM) energies ≳ 50 TeV, which would increase the cross-section of the interaction and the multiplicity of the interaction products, and lead to the composition of UHECRs appearing heavy-like. In this work, we study the effects of this scenario on the composition-sensitive cosmic-ray observables using EAS simulations for primaries in the energy region 1017 − 1020 eV. For that we produce a model for the transition from Galactic to extragalactic primaries, assuming a mixed composition Galactic and a single composition extragalactic component. We perform simulations for showers induced by each different primary species using the CORSIKA software, appropriately modified to include the new effects for first collisions at CM energies > 50 TeV, and study the observables produced by them. We find that the new effect reproduces perfectly the data from Pierre Auger Observatory for a proton-Air cross-section of ∼ 740 mb and an increase in first-collision products of a factor of 3, at 140 TeV CM energy
|