Searching for New Physics with Ultrahigh Energy Cosmic Rays

TL;DR

This paper explores how ultrahigh energy cosmic rays can be used to detect tiny violations of Lorentz invariance, providing constraints that impact quantum gravity theories.

Contribution

It presents the first constraints on Lorentz invariance violation using ultrahigh energy cosmic ray data from the Pierre Auger Observatory.

Findings

Derived a new upper limit on LIV parameter of 4.5 x 10^{-23}.

Used latest cosmic ray data to test Lorentz invariance.

Discussed future detection techniques for LIV searches.

Abstract

Ultrahigh energy cosmic rays that produce giant extensive showers of charged particles and photons when they interact in the Earth's atmosphere provide a unique tool to search for new physics. Of particular interest is the possibility of detecting a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of $\sim 10^{-35}$m. We discuss here the possible signature of Lorentz invariance violation on the spectrum of ultrahigh energy cosmic rays as compared with present observations of giant air showers. We also discuss the possibilities of using more sensitive detection techniques to improve searches for Lorentz invariance violation in the future. Using the latest data from the Pierre Auger Observatory, we derive a best fit to the LIV parameter of $3.0^{+1.5}_{-3.0} \times 10^{-23}$, corresponding to an upper limit of $4.5 \times 10^{-23}$ at a proton Lorentz factor of $\sim 2 \times 10^{11}$. This result has fundamental implications for quantum gravity models.