Light-by-light scattering with intact protons at the LHC: from Standard Model to New Physics

TL;DR

This paper explores the potential of the LHC to detect light-by-light scattering induced by the Standard Model and new charged particles, using intact proton detection and model-independent bounds to identify new physics signatures.

Contribution

It introduces a simulation method for model-independent bounds on massive charged particles via light-by-light scattering at the LHC, including the implementation of full four-photon amplitudes for various spins.

Findings

Vector particles with Q_eff=4 detectable up to 640 GeV

Fermions with Q_eff=4 detectable up to 300 GeV

Sensitivity to heavy neutral particles in the multi-TeV range

Abstract

We discuss the discovery potential of light-by-light scattering at the Large Hadron Collider (LHC), induced by the Standard Model (SM) and by new exotic charged particles. Our simulation relies on intact proton detection in the planned forward detectors of CMS and ATLAS. The full four-photon amplitudes generated by any electrically charged particles of spins $1/2$ and $1$, including the SM processes involving loops of leptons, quarks and $W$ bosons are implemented in the Forward Physics Monte Carlo generator. Our method provides model-independent bounds on massive charged particles, only parametrized by the spin, mass and "effective charge" $Q_{\rm eff}$ of the new particle. We find that a new charged vector (fermion) with $Q_{\rm eff}=4$ can be discovered up to $m=640~\rm GeV$ ($m=300~\rm GeV$) with an integrated luminosity of $300~\rm fb^{-1}$ at the LHC. We also discuss the sensitivities to neutral particles such as a strongly-interacting heavy dilaton and warped Kaluza-Klein gravitons, whose effects could be discovered for masses in the multi-TeV range.