Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays - Astrophysics

Abstract: There has been much interest in possible violations of Lorentz invariance,particularly motivated by quantum gravity theories. It has been suggested thata small amount of Lorentz invariance violation LIV could turn off photomesoninteractions of ultrahigh energy cosmic rays UHECRs with photons of thecosmic background radiation and thereby eliminate the resulting sharpsteepening in the spectrum of the highest energy CRs predicted by GreisenZatsepin and Kuzmin GZK. Recent measurements of the UHECR spectrum reportedby the HiRes and Auger collaborations, however, indicate the presence of theGZK effect. We present the results of a detailed calculation of themodification of the UHECR spectrum caused by LIV using the formalism of Colemanand Glashow. We then compare these results with the experimental UHECR datafrom Auger and HiRes. Based on these data, we find a best fit amount of LIV of$4.5^{+1.5} {-4.5} \times 10^{-23}$,consistent with an upper limit of $6 \times10^{-23}$. This possible amount of LIV can lead to a recovery of the cosmic rayspectrum at higher energies than presently observed. Such an LIV recoveryeffect can be tested observationally using future detectors.

Author: S. T. Scully JMU, F. W. Stecker NASA-GSFC

Source: https://arxiv.org/