Search for light-speed anisotropies using Compton scattering of high-energy electrons

TL;DR

This study uses high-energy Compton scattering data to search for possible anisotropies in the speed of light, setting new stringent limits on Lorentz invariance violation.

Contribution

It introduces a novel method using Compton scattering off ultra-relativistic electrons to constrain light-speed anisotropies, improving previous bounds by an order of magnitude.

Findings

No sidereal variations detected in Compton-edge photon energies

Set a new upper limit of 1.6 x 10^{-14} on Lorentz violation parameters

Provides the most stringent constraints to date on light-speed anisotropies

Abstract

Based on the high sensitivity of Compton scattering off ultra relativistic electrons, the possibility of anisotropies in the speed of light is investigated. The result discussed in this contribution is based on the gamma-ray beam of the ESRF's GRAAL facility (Grenoble, France) and the search for sidereal variations in the energy of the Compton-edge photons. The absence of oscillations yields the two-sided limit of 1.6 x 10^{-14} at 95 % confidence level on a combination of photon and electron coefficients of the minimal Standard Model Extension (mSME). This new constraint provides an improvement over previous bounds by one order of magnitude.