No abstract

We search for neutral heavy leptons that are isosinglets under the standard SU (2)l gauge group. Such neutral heavy leptons are expected in many extensions of the standard model. Three types of heavy leptons Ne, N^, NT associated with the three neutrino types v* have been directly searched for and no evidence for a signal has been found. We set the limit Br(Z° -► z//N*) < 3 x 10" 5 at the 95% CL for the mass range from 3 GeV up to m%.

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The results of the searches for neutral Higgs boson production in the process e+e---+ Z* Ho are reported, focusing on Higgs boson masses below 70 GeV. The data sample consists of three million hadronic Z" decays collected by the L3 experiment at LEP from 1991 through 1994. No signal is found leading to a lower limit on the mass of the Standard Model Higgs boson of 60.2 GeV at 95% C.L.These results are also interpreted in the framework of the General Two Doublet Model and limits on the nonstandard Higgs boson production through the process e + -e 4 Z* ho are set. A lower limit of 66.7 GeV at 95% CL. is obtained for the case where the Higgs decays into an invisible final state.

0370-2693r98r$ -see front matter q 1998 Elsevier Science B.V. All rights reserved.Ž . PII: S 0 3 7 0 -2 6 9 3 9 8 0 0 7 3 6 -9 ( ) M. Acciarri et al.r Physics Letters B 434 1998 169- AbstractWe analyse e q e y ™ ttg events using 100 pb y1 of data collected by the L3 experiment during the 1991-1995 LEP runs at the Z pole. From the energy of the photons and their isolation from the tau decay products, we determine the anomalous magnetic and electric dipole moments of the tau to be, respectively: a s 0.004 " 0.027 " 0.023; t d s 0.0 " 1.5 " 1.3 = 10 y16 e P cm. Ž .t This is a direct measurement of these t form factors at q 2 s 0. q 1998 Elsevier Science B.V. All rights reserved.