A theoretical study suggests that a future high-energy muon collider could be an exceptional tool for investigating charged lepton-flavor violation (LFV). This phenomenon, forbidden in the Standard Model of particle physics, would involve the transformation of one type of charged lepton (like a muon) into another (like an electron or a tau). The research focuses on dimension-six four-lepton operators within the Standard Model Effective Field Theory (SMEFT).

The researchers analyzed processes such as μ⁺μ⁻ → e⁺τ⁻, μ⁺μ⁻ → e⁺μ⁻, and μ⁺μ⁻ → μ⁺τ⁻ at center-of-mass energies of 3, 10, and 14 TeV. Key factors like beam polarization and hadronic tau reconstruction were incorporated. Using an optimal-observable analysis of the angular distributions, a global fit to the relevant set of four-lepton operators was performed. The results project sensitivities for the C/Λ² coefficients in the range of (0.6-1.6) × 10⁻¹¹ GeV⁻², depending on the flavor and chiral structure of the operator. These sensitivities exceed current limits by up to an order of magnitude.

The study emphasizes that a combined analysis of multiple center-of-mass energies and beam polarizations would significantly improve the resolution of correlations among the Wilson coefficients. This highlights the strong capability of a future multi-TeV muon collider to probe charged lepton flavor violating interactions, establishing it as a powerful tool for exploring the SMEFT parameter space and searching for new physics beyond the Standard Model.