Lepton flavor physics at μ+μ+ colliders

Abstract

We discuss sensitivities to lepton flavor violating (and conserving) interactions at future muon colliders, especially at μ+μ+ colliders. Compared with the searches for rare decays of μ and τ, we find that the TeV-scale future colliders have better sensitivities depending on the pattern of hierarchy in the flavor mixings. As an example, we study the case with the type-II seesaw model, where the flavor mixing parameters have direct relation to the neutrino mass matrix. At a μ+μ+ collider, the number of events of the μ+μ+ → μ+τ+ process can be larger than mathcal{O}(100) with the center of mass energy sqrt{s} = 2 TeV, and with an integrated luminosity mathcal{L} = 1 ab−1, while satisfying bounds from rare decays of μ and τ. We discuss impacts of the overall mass scale of neutrinos as well as CP violating phases to the number of expected events.