Future prospects of testing Lorentz invariance with UHECRs

Understand

In the last years a general consensus has emerged on the use of ultra-high energy cosmic rays (UHECR) data as a powerful probe of the validity of special relativity.

• This applies in particular to the propagation of cosmic rays from their sources to Earth, responsible for energy suppressions due to pion photoproduction by UHE protons (the Greisen-Zatsepin Kuzmin limit) and photo disintegration of UHE nuclei (the Gerasimova-Rozental limit).
• A suppression in the flux of UHECRs at energies above 40 EeV -- as expected from both these interactions -- has been established experimentally beyond any doubt by current experiments.
• However, such an observation is still not conclusive on the origin of the suppression.