Lepton flavor violation in photon-induced electron-muon pairs at the HL-LHC

Abstract

We show the outstanding potential of the High-Luminosity LHC (HL-LHC) to discover charged lepton flavor violation (cLFV) via the ultra-peripheral process $\gamma\gamma \to e^\pm\mu^\mp$. Using a gauge-invariant Effective Field Theory (EFT) framework -consistent with the most stringent bounds from radiative decays- we perform a full Monte Carlo analysis with multivariate techniques. Our results show that a $5\sigma$ discovery is achievable with an integrated luminosity of $\mathcal{L}_{\rm int} \gtrsim 2700$ fb$^{-1}$ for favorable benchmark scenarios. This study establishes photon-fusion at the HL-LHC as a powerful probe of cLFV, strongly motivating dedicated searches by the experimental collaborations.