Bounds on charged lepton mixing with exotic charged leptons

摘要

We examine the effects of mixing induced light heavy charged lepton neutral currents on the partial wave amplitude for the process l~+l~- → ZZ (with l = e, μ or τ). By imposing the constraints that the amplitude should not exceed the perturbative unitarity limit at high energy (s~(1/2) = Λ), we obtain bounds on light heavy charged lepton mixing parameter sin~2 (2θ_L~a) where θ_L~a is the mixing angle of the ordinary charged lepton with its exotic partner. For Λ = 1 TeV, no bound is obtained on sin~2(2θ_L~a) for m_E < 0.69 TeV. However, sin~2 (2θ_L~a) ≤ 1.52 x 10~(-5) for m_E = 5 TeV, sin~2 (2θ_L~a) ≤ 2.41 x 10~(-7) for m_E = 10 TeV. Similarity for Λ = ∞ no bound is obtained on sin~2 (2θ_L~a) for m_E < 1.97 TeV and sin~2 (2θ_L~a) ≤ 0.15 for m_E = 5 TeV and sin~2 (2θ_L~a) ≤ 3.88 x 10~(-2) for m_E = 10 TeV.