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

Nayantara Gupta

doi:10.1016/j.physletb.2003.11.044

Abstract

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 4×1019 eV. We present in this Letter 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.

Highlights

The clustering of ultra high energy cosmic ray events suggests that they have originated from compact sources
The authors of [26] have shown that there is a significant correlation between compact sources and observed ultra high energy cosmic ray events using the data from Akeno Giant Air Shower Array (AGASA) [3] and Yakutsk [4] experiments
The still unknown data from HiRes experiment [2] and the accumulating data from AUGER experiment [31] will enable us to carry out statistical analysis with a bigger set of data in the near future. As of it is not clear whether the ultra high energy cosmic rays (UHECR) events are statistically uncorrelated with compact sources at high redshifts, the physical mechanisms by which neutral component of UHECR may come to the Earth evading the GZK cut-off from high redshifts are still exciting fields of study for us

Summary

Introduction

The clustering of ultra high energy cosmic ray events suggests that they have originated from compact sources. The composition of the ultra high energy cosmic rays (UHECR) has been studied in [8, 10]. It was pointed out by Dubovsky et al [29] that the statistics of clustering of ultra high energy cosmic ray events suggests their correlation with compact sources.

Results

Conclusion