Lorentz Invariance Violation and Chemical Composition of Ultra High Energy Cosmic Rays

TL;DR

This paper investigates how Planck-scale Lorentz Invariance Violation could affect the propagation and composition of ultra high energy cosmic rays, providing constraints on LIV parameters based on observed heavy nuclei presence.

Contribution

It introduces a formalism linking LIV effects to cosmic ray nuclei photodisintegration and derives new constraints on LIV parameters from cosmic ray composition data.

Findings

Constraints on LIV parameter η for different nuclei: Fe, O, He.

LIV effects can significantly influence cosmic ray propagation.

Heavy nuclei presence at high energies constrains LIV models.

Abstract

Motivated by experimental indications of a significant presence of heavy nuclei in the cosmic ray flux at ultra high energies ($\gtrsim 10^{19} \eV$), we consider the effects of Planck scale suppressed Lorentz Invariance Violation (LIV) on the propagation of cosmic ray nuclei. In particular we focus on LIV effects on the photodisintegration of nuclei onto the background radiation fields. After a general discussion of the behavior of the relevant quantities, we apply our formalism to a simplified model where the LIV parameters of the various nuclei are assumed to kinematically result from a single LIV parameter for the constituent nucleons, $\eta$, and we derive constraints on $\eta$. Assuming a nucleus of a particular species to be actually present at $10^{20}$ eV the following constraints can be placed: $-3\times10^{-2} \lesssim \eta \lesssim 4$ for $^{56}$Fe, $-2\times10^{-3} \lesssim \eta \lesssim 3\times10^{-2}$ for $^{16}$O and $-7\times10^{-5} \lesssim \eta \lesssim 1\times10^{-4}$ for $^{4}$He, respectively.