Search for Charged Higgs Bosons in e+e- Collisions at \sqrt{s} = 189 GeV

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at a centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 176.4 pb^-1. Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed events are consistent with the expectations from Standard Model background processes. A lower limit of 65.5 GeV on the charged Higgs mass is derived at 95 % confidence level, independent of the decay branching ratio Br(H^{+/-} -> tau nu)

Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP

We report on measurements of the triple-gauge-boson couplings of the W boson in $\mathrm{e^+e^-}$ collisions with the L3 detector at LEP. W-pair, single-W and single-photon events are analysed in a data sample corresponding to a total luminosity of 76.7~pb$^{-1}$ collected at centre-of-mass energies between 161~GeV and 183~GeV. CP-conserving as well as both C- and P-conserving triple-gauge-boson couplings are determined. The results, in good agreement with the Standard-Model expectations, confirm the existence of the self coupling among the electroweak gauge bosons and constrain its structure

A Measurement of Pi-Polarization at Lep

Contains fulltext : 26223.pdf (publisher's version ) (Open Access

Electroweak parameters of the z0 resonance and the standard model

Contains fulltext : 124399.pdf (publisher's version ) (Open Access

Hard-photon production and tests of QED at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

The total and differential cross sections of the process e(+)e(-) --> n gamma with n greater than or equal to 2 are measured using data collected by the L3 experiment at centre-of-mass energies of root s = 183 and 189 GeV, The results are in agreement with the Standard Model expectations. Limits are set on deviations from QED, contact interaction cut-off parameters and masses of excited electrons. (C) 2000 Published by Elsevier Science B.V. All rights reserved

Measurement of the cross-section for the process gamma*gamma* -> hadrons at LEP

Measurements of the two-photon interaction e(+)e(-) --> e(+)e(-) + hadrons at root s similar or equal to 91 GeV and root s similar or equal to 183 GeV are presented. The double-tag events, collected with the L3 detector, correspond to integrated luminosities of 140 pb(-1) at 91 GeV and 52 ph(-1) at 183 GeV. The cross-section of gamma*gamma* collisions has been measured at [Q(2)] = 3.5 GeV2 and [Q(2)] = 14 GeV2. The data agree well with predictions based on perturbative QCD, while the Quark Parton Model alone is insufficient to describe the data. (C) 1999 Published by Elsevier Science B.V. All rights reserved

Study of neutral-current four-fermion and ZZ production in e(+)e(-) collisions at root s=183GeV RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

A study of neutral-current four-fermion processes is performed using a data sample corresponding to 55.3 pb(-1) of integrated luminosity collected by the L3 detector at LEP at an average centre-of-mass energy of 183 GeV. The neutral-current four-fermion cross sections for final slates with a pair of charged leptons plus jets and with four charged leptons are measured to be consistent with the Standard Model predictions. Events with fermion pair masses close to the Z boson mass are selected in all observable final states and the ZZ production cross section is measured to be sigma ZZ = 0.30(-0.16-0.03)(+0.22 + 0.07) pb, in agreement with the Standard Model expectation. No evidence for the existence of anomalous triple gauge boson ZZZ and ZZ gamma couplings is found and limits on these couplings are set. (C) 1999 Elsevier Science B.V. All rights reserved