A new limit on the light speed isotropy from the GRAAL experiment at the ESRF

TL;DR

This study uses Compton scattering at ESRF to perform a one-way test of light speed isotropy, providing new constraints that improve upon previous limits and supporting the consistency of relativistic kinematics.

Contribution

It introduces a novel method using Compton Edge measurements at ESRF for testing light speed isotropy, achieving more stringent limits than prior experiments.

Findings

Improved limits on light speed isotropy from GRAAL-ESRF data.

Validation of relativistic kinematics through one-way light speed tests.

Demonstrated the effectiveness of using Compton Edge measurements for fundamental physics tests.

Abstract

When the electrons stored in the ring of the European Synchrotron Radiation Facility (ESRF, Grenoble) scatter on a laser beam (Compton scattering in flight) the lower energy of the scattered electron spectra, the Compton Edge (CE), is given by the two body photon-electron relativistic kinematics and depends on the velocity of light. A precision measurement of the position of this CE as a function of the daily variations of the direction of the electron beam in an absolute reference frame provides a one-way test of Relativistic Kinematics and the isotropy of the velocity of light. The results of GRAAL-ESRF measurements improve the previously existing one-way limits, thus showing the efficiency of this method and the interest of further studies in this direction.