Search for excited leptons in e+e− annihilation at s=161 GeV

A search for excited leptons e∗, μ∗, τ∗ and νe∗ in e+e− collisions at s=161 GeV is performed using the 10.8 pb−1 of data collected by the L3 detector at LEP. No evidence has been found for their existence. From an analysis of the expected ℓ∗ℓ∗ pair production in the channels eeγγ, μμγγ, ττγγ, eeWW, and ννγγ, the lower mass limits at 95% C.L. are 79.7 GeV for e∗, 79.9 GeV for μ∗, 79.3 GeV for τ∗ and 71.2 GeV for νe∗ assuming the same couplings as for standard leptons. From an analysis of the expected ℓℓ∗ single production in channels eeγ, μμγ, ττγ, νeeW and ννγ, the upper limits on the couplings λmℓ∗ up to mℓ∗ = 161 GeV are determined.