Observability of neutron events above the Greisen-Zatsepin-Kuzmin cut-off due to violation of Lorentz invariance

The clustering of ultra high energy cosmic ray events suggests that they have originated from compact sources. One of the possible physical mechanisms by which ultra high energy nuclei reach the Earth from far away astrophysical sources (quasars or BL Lac objects) evading the Greisen-Zatsepin-Kuzmin (GZK) cut-off is by violation of Lorentz invariance. Assuming that there is violation of Lorentz invariance, we calculate the expected number of neutron events from some of the EGRET sources (including γ-ray loud BL Lac objects) which can be correlated in direction with ultra high energy cosmic ray events observed by AGASA above energy 4× 10eV. We present in this paper what AGASA should see in future if violation of Lorentz invariance is responsible for the propagation of ultra high energy cosmic rays having energies above the GZK cut-off when there is a correlation of EGRET sources with the ultra high energy cosmic ray events. PACS numbers:11.30.Cp, 98.54.-h, 96.40.-z Observational data on ultra high energy cosmic ray events have been recorded by different experiments like Fly’s Eye [1, 2], Akeno Giant Air Shower Array (AGASA) [3], Yakutsk experiment [4], Haverah Park [5], Volcano Ranch experiment [6] and Sydney University Giant Air-shower Recorder (SUGAR) [7]. The composition of the ultra high energy cosmic rays (UHECR) has been studied in [8, 10]. Data from Fly’s Eye experiment [8] suggest that the chemical composition is dominated by heavy nuclei up to ankle (10)eV and thereafter by lighter component like protons. The AGASA data [10] suggest a mixed composition of both protons and heavier nuclei. The present experiments do not give us enough information about the chemical composition of primary UHECR. This topic has been addressed in [11]. If the UHECR are nuclei, then what could be their origin and how they propagate in the extragalactic Email address: [email protected]