Probing Lorentz symmetry with the Pierre Auger Observatory

Effects of Lorentz invariance violation (LIV) can be present at energies much lower than the quantum gravity scale. Here the possible LIV effects in ultra-high energy cosmic rays (UHECRs) are investigated. To this aim, modifications of the propagation of UHECR protons and nuclei in the extragalactic space due to LIV effects are taken into account. For the first time a fit of both flux and composition of UHECRs as measured by the Pierre Auger Observatory is used in order to evaluate the constraining power of current data on LIV parameters.