2026/07/28 by Sukanta Dutta, Purnath Unnikrishnan, Yashasvi
#hep-ph #hep-ex
We investigate charged lepton-flavour violation (LFV) induced by dimension-six four-lepton operators within the Standard Model Effective Field Theory at a proposed high-energy muon collider. We study the processes μ+μ-→ e±τ∓, μ+μ-→ e±μ∓, and μ+μ-→ μ±τ∓ at √(s)=3, 10, and 14~TeV, incorporating beam polarisation and hadronic τ reconstruction. Using an optimal-observable analysis of the angular distributions, we perform a global fit to the relevant set of four-lepton operators. Projected sensitivities reach C/Λ2∼(0.6-1.6)×10-11 GeV-2, depending on the flavour and chiral structure of the operator, exceeding current limits by up to an order of magnitude. A combined analysis of multiple centre-of-mass energies and beam polarisations significantly improves the resolution of correlations among the Wilson coefficients. These results highlight the strong sensitivity of a future multi-TeV muon collider to charged lepton flavour violating four-lepton interactions, establishing it as a powerful probe of the SMEFT parameter space.