We have analyzed one-prong r decays with neutral kaons using the information from a fine-grained hadron calorimeter. The data sample consists of 43 500 Z 7-V~(y) events collected by the L3 detector at LEP in 1991, 1992 and 1993. The following branching fractions are measured: B(t~~ —+ iy7r“ K°) = 0.0095 ± 0.0015(stat) ± 0.0006(syst); B ( t —> vrir " 7r°K°) = 0.0041 ± 0.0012(stat) ± 0.0003(syst) and 2?(r' -> pTir~K°K°) = 0.0031 ± 0.0012(stat) ± 0.0004(syst).

A search for exclusive decays of B[] and mesons has been performed in the channels ̂ J77, Bj —+ J77, Bj —» J7r° and Bs —► J7t°. The data sample consisted of more than three and half million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90% confidence level: 3.2 x 10~4 on Br(B^ -► J7r°) and the first experimental limits: Br(B° -+ J77) < 1.2 x 10\ Br(Bs -> J77) < 3.8 x 10“ 3, Br(B° -> h r°) < 1.2 x 10-3 .

We present evidence for soft gluon interference, as required by QCD. This interference is expected to manifest itself in an angular ordering of the gluons radiated within a jet. Using hadronic decays of the Z boson in the L3 detector at LEP, we compare variables sensitive to such an angular ordering, namely the energy-energy correlation asymmetry and the newly introduced particle-particle correlation asymmetry, with the predictions of various parton shower models. Only those models which incorporate the expected interference agree with the data.

Using the data collected with the L3 detector at LEP between 1990 and 1995, corresponding to an integrated luminosity of 149 pb(-1), the tau longitudinal polarisation has been measured as a function of the production polar angle using the tau decays tau(-) --> h(-)nu(tau) (h = pi,rho,a(1)) and tau(-)-->l(-)<(nu)over bar>(l)nu(tau) (l = e,mu). From this measurement the quantities A(c) and A(tau), which depend on the couplings of the electron and the tau to the Z, are determined to be A(c) = 0.1678 +/- 0.0127 +/- 0.0030 and A(tau) = 0.1476 +/- 0.0088 +/- 0.0062, consistent with the hypothesis of e-tau universality, Under this assumption a value of A(l) = 0.1540 +/- 0.0074 +/- 0.0044 is obtained, yielding the value of the effective weak mixing angle sin(2)<(theta)over bar>(W) = 0.2306 +/- 0.0011. (C) 1998 Elsevier Science B.V. All rights reserved.

Time-dependent B-0-(B) over bar(0) mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of B-d(0) meson oscillations isDelta m(d) = 0.444 +/- 0.040 ps(-1).

Events characterised by large hadronic energy and transverse momentum are selected from the data collected by the L3 detector at LEP at centre-of-mass energies between 161 and 172 GeV, corresponding to an integrated luminosity of 21 pb(-1) The visible mass and the missing mass distributions of the selected events are consistent with those expected from Standard Model processes. This result is combined with that from data taken at the Z resonance to sci an upper limit on the production rate and decay into invisible final states of a non-minimal Higgs boson. as a function of the Higgs mass. Assuming the non-minimal Higgs production cross section to be the same as for the Standard Model Higgs boson and the decay branching fraction into invisible final states to be 100%, a Higgs mass lower limit of 69.6 GeV is derived at 95% confidence level. (C) 1998 Elsevier Science B.V.

Time-dependent B-B̄ mixing is studied using about two million hadronic Z decays registered by L3 in 1994 and 1995. For this study three techniques are used. Tagging of the b-quark charge at decay time is performed by identifying leptons from semileptonic B decays. The flavour of the b quark at production time is determined from the charge of the lepton in the opposite hemisphere or by using a jet-charge technique. The proper time of the B-particle decay is obtained by reconstructing the production and decay vertices or by a measurement of the lepton impact parameter. The combined result for the frequency of Bd meson oscillations is ∆md = 0.444 ± 0.040 ps−1. The L3 Collaboration: Measurement of the Bd − B̄d oscillation frequency 197

The formation of the eta' in the reaction e(+)e(-)-->e(+)e(-)eta'-->e(+)e(-)pi(+)pi(-)gamma has been measured by the L3 detector at a centre-of-mass energy of 91 GeV. The radiative width of the eta' has been found to be Gamma(gamma gamma)=4.17+/-0.10(stat.)+/-0.27(sys.)keV. The Q(2) dependence of the eta' formation cross section has been measured for Q(2) less than or equal to 10 GeV2 and the eta' electromagnetic transition form factor has been determined. The form factor can be parametrised by a pole form with Lambda=0.900+/-0.046(stat.)+/-0.022(sys.)GeV. It is also consistent with recent non-perturbative QCD calculations. (C) 1998 Elsevier Science B.V.

Local multiplicity fluctuations in hadronic Z decays are studied using the L3 detector at LEP. Bunching parameters are used for the first time in addition to the normalised factorial moment method. The bunching parameters directly demonstrate that the fluctuations in rapidity are multifractal. Monte Carlo models show agreement with the data, reproducing the trend, although not always the magnitude, of the factorial moments and bunching parameters. (C) 1998 Elsevier Science B.V. All rights reserved.

The measurements of hadron and lepton-pair production cross sections and lepton-pair forward-backward asymmetries performed with the L3 detector at centre-of-mass energies between 130 GeV and 172 GeV are used to search for new physics phenomena. New physics effects involving four fermion vertices - contact interactions - are looked for in all channels. For hadron production the exchange of virtual leptoquarks and scalar quarks is studied. No evidence for deviations from the Standard Model expectations is found. Lower limits on the scale Lambda of contact interactions in the range 1.2-7.1 TeV are obtained at the 95% confidence level for various models. Upper limits on the coupling strengths of leptoquarks and scalar quarks are derived. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

Local multiplicity fluctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at root s similar or equal to 91.2 GeV, which were collected by the L3 detector at LEP. Parton shower Monte Carlo programs agree well with the data. On the other hand, first-order QCD calculations in the Double Leading Log Approximation and the Modified Leading Log Approximation are found to deviate significantly from the data, (C) 1998 Elsevier Science B.V. All rights reserved.

LEP measurements of the weak electric dipole moment dwτ and the weak anomalous magnetic dipole moment aωτ of the τ lepton are reviewed and the search for CP violation in the production of τ pairs on the Z peak is discussed. Two methods of the measurement of the weak dipole moments based on the analysis of the transverse and normal components of single τ polarisation (azimuthal asymmetries) and spin-spin correlations (optimal observables) are discussed. Averaging the LEP measurements, upper limits on the weak electric dipole moment of the τ lepton are obtained.

A determination of the number of light neutrino families performed by measuring the cross section of single photon production in e(+)e(-) collision near the Z resonance is reported. From an integrated luminosity of 100 pb(-1), collected during the years 1991-94, we have observed 2091 single photon candidates with an energy above 1 GeV in the polar angular region 45 degrees < theta(gamma) < 135 degrees. From a maximum likelihood fit to the single photon cross section, the Z decay width into invisible particles is measured to be Gamma(inv) = 498 +/- 12(stat) +/- 12(sys)MeV. Using the Standard Model couplings of neutrinos to the Z, the number of light neutrino species is determined to be N-v = 2.98 +/- 0.07(stat) +/- 0.07(sys). (C) 1998 Published by Elsevier Science B.V. All rights reserved.

We have searched for evidence of T production in 3.5 million hadronic Z decays collected by the L3 detector at LEP in 1991-1995. No signals are observed for the decay chain Z �� ��X; T �� ? +? - (?= e,��), therefore upper limits at the 95% confidence level are set on the following Z branching fractions: Br(Z �� ��(1S)X) < 5.5 �� 10 -5; Br(Z �� ��(2S)X) < 13.9 �� 10 -5; Br(Z �� ��(3S)X) < 9.4 �� 10 -5. Published by Elsevier Science B.V.

We report on the measurement of W-boson pair-production with the L3 detector at LEP at an average centre-of-mass energy of 172.13 GeV. In a data sample corresponding to a total luminosity of 10.25 pb−1 we select 110 four-fermion events with pairs of hadronic jets or leptons with high invariant masses. Branching fractions of W decays into different fermion-antifermion pairs are determined with and without the assumption of charged-current lepton universality. The branching fraction for hadronic W decays is measured to be: B(W → hadrons) = 64.2−3.8+3.7 (stat.) ± 0.5 (syst.) %. Combining all final states the total cross section for W-pair production is measured to be: σWW = 12.27−1.32+1.41 (stat.) ± 0.23 (syst.) pb. The results are in good agreement with the Standard Model.

We present a study of the inclusive ω and η′ production based on 3.1 million hadronic Z decays recorded with the L3 detector at LEP during 1991–1994. The production rates per hadronic Z decay have been measured to be 1.17±0.17 ω mesons and 0.25±0.04 η′ mesons. The production rates and the differential cross sections have been compared with predictions of the JETSET and the HERWIG Monte Carlo models. We have observed that the differential cross sections can be described by an analytical quantum chromodynamics calculation.