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

Abstract A search for excited leptons e ∗ , μ ∗ , τ ∗ and ν e ∗ 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 ν e ∗ assuming the same couplings as for standard leptons. From an analysis of the expected ll ∗ single production in channels eeγ, μμγ, ττγ, ν e eW and ννγ, the upper limits on the couplings λ m l ∗ up to m l ∗ = 161 GeV are determined.