Search for excited leptons in e+e− collisions at

We have searched for excited states of charged and neutral leptons, e∗, μ ∗ , τ ∗ and ν ∗ , in e+e− collisions at s =130 using the OPAL detector at LEP. No evidence for their existence was found. With the most common coupling assumptions, the final states from excited lepton pair production include l+l−γγ and l+l−WW (with the subsequent decay of the virtual W bosons). From the analysis of these final states, 95% confidence level lower mass limits of 66.5 GeV for e∗, 66.8 GeV for μ ∗ , 65.3 GeV for τ ∗ , 66.2 GeV for ν e ∗ , 66.5 GeV for ν μ ∗ and 64.7 GeV for ν τ ∗ are inferred. From the analysis of γγ final states with missing energy and using alternative coupling assignments which permit photonic ν ∗ decays, a 95% confidence level lower mass limit of 65.0 GeV for each ν ∗ flavour is inferred. From the analysis of the l+l−γ, acoplanar lepton pair, and single γ final states expected from excited lepton single production, upper limits on f Λ (ratio of the coupling to the compositeness scale) are determined for excited lepton masses up to the kinematic limit.