Search for Excited Leptons in $e^+ e^-$ Annihilation at $\sqrt{s}$ = 161 GeV

A search for excited leptons $\rm e^*,~\mu^*, ~\tau^*$ and $\nu_{\rm e}^*$ in $\rm e^+e^-$ collisions at $\rm \sqrt{s}$ = 161 GeV is performed using the $\rm 10.8 ~pb^{-1}$ of data collected by the L3 detector at LEP. No evidence has been found for their existence. From an analysis of the expected $\ell^*\ell^*$ pair production in the channels $\rm ee\gamma\gamma$, $\rm \mu\mu\gamma\gamma$, $\rm \tau\tau\gamma\gamma$, $\rm eeWW$, and $\rm \nu\nu\gamma\gamma$, the lower mass limits at 95\% C.L. are 79.7 GeV for $\rm e^{*}$, 79.9 GeV for $\mu^{*}$, 79.3 GeV for $\tau^{*}$ and 71.3 GeV for $\nu_{\rm e}^{*}$ assuming the same couplings as for standard leptons. From an analysis of the expected $\ell\ell^*$ single production in channels $\rm ee\gamma$, $\mu\mu\gamma$, $ \tau\tau\gamma$, $\rm \nu_{e}eW$ and $\nu\nu\gamma$, the upper limits on the couplings $\lambda/m_{\ell^*}$ up to $m_{\ell^{*}}$ = 161 GeV are determined.