Constraints on Lorentz invariance violation using HAWC observations above 100 TeV

TL;DR

This paper uses high-energy gamma-ray observations from HAWC to set stringent limits on Lorentz Invariance Violation, surpassing previous constraints by over 60 times, thus testing fundamental physics at unprecedented energy scales.

Contribution

It introduces an energy-reconstruction algorithm for HAWC using neural networks and applies it to set new limits on LIV at energies above 100 TeV.

Findings

Limits on LIV energy scale > 10^31 eV

Constraints exceed previous bounds by over 60 times

Demonstrates HAWC's capability for high-energy astrophysics

Abstract

Due to the high energies and long distances involved, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz Invariance Violation (LIV). Superluminal LIV enables the decay of photons at high energy over relatively short distances, giving astrophysical spectra which have a hard cutoff above this energy. The High Altitude Water Cherenkov (HAWC) observatory is the most sensitive currently-operating gamma-ray observatory in the world above 10 TeV. Together with the recent development of an energy-reconstruction algorithm for HAWC using an artificial neural network, HAWC can make detailed measurements of gamma-ray energies above 100 TeV. With these observations, HAWC can limit the LIV energy scale greater than $10^{31}$ eV, over 800 times the Planck energy scale. This limit on LIV is over 60 times more constraining than the best previous value for $\rm E_{LIV}^{(1)}$.