Photon-photon physics at the LHC and laser beam experiments, present and future

TL;DR

This paper reviews photon-photon interactions at the LHC, focusing on light-by-light scattering, and explores future laser experiments to probe new physics beyond the standard model at high energies.

Contribution

It highlights the potential of LHC and laser beam experiments to study photon-photon interactions and search for signs of new physics such as extra dimensions.

Findings

Experimental evidence of light-by-light scattering at the LHC

Potential to detect deviations indicating new physics

Prospects for future laser-based photon-photon experiments

Abstract

Under certain running conditions, the CERN Large Hadron Collider (LHC) can be considered as a photon-photon collider. Indeed, in proton-proton, proton-ion, ion-ion collisions, when incoming particles pass very close to each other in very peripheral collisions, the incoming protons or ions remain almost intact and continue their path along the beam axis. Then, only the electromagnetic (EM) fields of these ultra-relativistic charged particles (protons or ions) interact to leave a signature in the central detectors of the LHC experiments. The interest is that the photon-photon interactions happen at unprecedented energies (a few TeV per nucleon pairs) where the quantum electrodynamics (QED) theory can be tested in extreme conditions and unforeseen laws of nature could be discovered. In this report, we propose a focus on a particular reaction, called light-by-light scattering in which two incoming photons interact, producing another pair of photons. We describe how experimental results have been obtained at the LHC. In addition, we discuss prospects for on-shell photon-photon interactions in dedicated laser beam facilities. Potential signatures of new physics might manifest as resonant deviations in the refractive index, induced by anomalous light-by-light scattering effects. Importantly, we explain how this process can be used to probe the physics beyond the standard model such as theories that include large extra dimensions. Finally, some perspectives and ideas are given for future data taking or experiments.