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

Abstract A search with the DELPHI detector at LEP for excited leptons( e ∗ , μ ∗ , τ ∗ and ν ∗ ) decaying through γ, W or Z transitions is reported. The data used correspond to an integrated luminosity of 10 pb −1 at an e + e − centre-of-mass energy of 161 GeV. The search for pair produced excited leptonsestablished the limits m e ∗ > 79.6 GeV /c 2 , m μ ∗ > 79.6 GeV /c 2 , m τ ∗ > 79.4 GeV /c 2 and m ν ∗ > 56.4 GeV /c 2 at 95% confidence level, assuming that the SU(2) and U(1) couplings of excited leptonsare in the same ratio as for normal leptonsand considering both left and right-handed components. Limits corresponding to other assumptions are also given. The search for single excited leptonproduction established upper limits on the ratio λ m l ∗ of the coupling of the excited leptonto its mass.