New test of Lorentz symmetry using ultrahigh-energy cosmic rays

TL;DR

This paper proposes a novel method to test Lorentz symmetry by detecting coincident air showers from cosmic ray fragments disintegrated by solar photons, potentially constraining Lorentz violations with current observatories.

Contribution

It introduces a new observational approach using simultaneous air showers to test Lorentz symmetry, feasible with existing cosmic ray detectors.

Findings

Cross-correlation of showers is background free below 3° angular scale.

Detection of a few events can constrain Lorentz violating dispersion relations.

Solar photo-disintegration probability influences the feasibility of the test.

Abstract

We propose an innovative test of Lorentz symmetry by observing pairs of simultaneous parallel extensive air showers produced by the fragments of ultrahigh-energy cosmic ray nuclei which disintegrated in collisions with solar photons. We show that the search for a cross-correlation of showers in arrival time and direction becomes background free for an angular scale < 3^\circ and a time window {\cal O}(10 s). We also show that if the solar photo-disintegration probability of helium is {\cal O} (10^{-5.5}) then the hunt for spatiotemporal coincident showers could be within range of existing cosmic ray facilities, such as the Pierre Auger Observatory. We demonstrate that the actual observation of a few events can be used to constrain Lorentz violating dispersion relations of the nucleon.