Exploring Lorentz Invariance Violation from Ultra-high-energy Gamma Rays Observed by LHAASO

TL;DR

This paper analyzes ultra-high-energy gamma-ray data from LHAASO to test for Lorentz invariance violation, setting new lower bounds on LIV energy scales based on the absence of spectral cutoffs.

Contribution

It provides the first constraints on LIV using PeV gamma-ray observations, improving previous limits by an order of magnitude.

Findings

No LIV signature detected in gamma-ray spectra.

Lower limit on first-order LIV scale exceeds 10^5 times the Planck scale.

Second-order LIV scale is greater than 10^{-3} times the Planck scale.

Abstract

Recently the LHAASO Collaboration published the detection of 12 ultra-high-energy gamma-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV gamma rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy gamma rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 10^5 times the Planck scale M_{pl} and that the second-order LIV scale is >10^{-3}M_{pl}. Both limits improve by at least one order of magnitude the previous results.