The two-photon collision reaction e+e~ e+e~/+/~ has been studied at y/s ~ 91 GeV using the L3 detector at LEP for / = e, (i, r. We have analysed untagged configurations where the two photons are quasi-real. Good agreement is found between our measurements and the ö ( a 4) QED expectation. © 1997 Elsevier Science B.V.

We have measured the time integrated B°-B° mixing parameter and the forward-backward asymmetry in the process e+e~ 4bb using hadronic events containing muons or electrons. The data sample corresponds to 1,044,000 hadronic decays of the Z. From a fit to the momentum and transverse momentum distributions for single lepton and dilepton events, we have determined the Bu-B° mixing parameter to be XB = 0.123 ± 0.012 (stat.) ± 0.008 (sys.), and the bb forward-backward asymmetry at the effective center-of-mass energy \/s = 91.30GeV to be A b5 = 0.087_± 0.011 (stat.) ±0.004 (sys.) This measurement corresponds to a value of the effective electroweak mixing angle of sin20w = 0.2335 ± 0.0021. Dedicated to the memory of Professor Salvatore Lanzano

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.

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Using the L3 detector, the branching ratio BR(b --~ ~-uX) has been measured using a sample of Z --~ bl~ events tagged by high momentum and high transverse momentum leptons in one hemisphere and with missing energy in the opposite hemisphere. From a sample of 948 000 hadromc events we find BR(b ~ ~'~,X) = (2.4 ± 0.7 (stat.) 40.8 (syst.))%.

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Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.

We report measurements of the inclusive production of heavy quarkonium states in Z decays based on the analysis of 3.6 million hadronic events collected by the L3 detector at LEP. The measurement of inclusive J production and an improved 95% confidence level upper limit on gamma production are presented. In addition, two independent measurements of the ratio, f(p), Of prompt J mesons to those from B decay are made using two different isolation cuts to separate prompt J mesons from J mesons produced in the decays of b hadrons. The results are: Br(Z --> J + X) = (3.21 +/- 0.21 (stat.)(-0.28)(+0.19) (sys.)) X 10(-3) Br(Z --> gamma(1S) + X) < 4.4 x 10(-5), f(p) = (7.1 +/- 2.1 (stat.) +/- 1.2 (sys.)(-0.8)(+1.5) (theo.)) X 10(-2). (C) 1999 Published by Elsevier Science B.V. All rights reserved.

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.

New measurements at a centre-of-mass energy root s similar or equal to 183 GeV of the hadronic photon structure function F-2(gamma)(x) in the Q(2) interval, 9 GeV2 less than or equal to Q(2) less than or equal to 30 GeV2, are presented. The data, collected in 1997 with the L3 detector, correspond to an integrated luminosity of 51.9 pb(-1). Combining with the data taken at a centre-of-mass energy of 91 GeV, the evolution of F-2(gamma) With Q(2) is measured in the Q(2) range from 1.2 GeV2 to 30 GeV2. F-2(gamma) shows a linear growth with ln Q(2); the value of the slope alpha(-1)d F-2(gamma)(Q(2))/dlnQ(2) is measured in two x bins from 0.01 to 0.2 and is somewhat higher than predicted. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

Two-photon formation of the charmonium resonance chi(c2), has been studied with the L3 detector at LEP. The chi(c2) is identified through its decay chi(c2) --> gamma J/psi, with a subsequent decay J/psi --> e(+)e(-) or J/psi --> mu(+)mu(-). With an integrated luminosity of 140 pb(-1) at root s similar or equal to 91 GeV and 52 pb(-1) at root s similar or equal to 183 GeV, we measure the two-photon width of the chi(c2) to be Gamma(gamma gamma)(chi(c2)) = 1.02 +/- 0.40 (stat.) +/- 0.15 (sys.) +/- 0.09(BR.) keV. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

The time-integrated B-0(B) over bar(0) mixing parameter and the forward-backward charge asymmetry in the process e(+)e(-) --> b (b) over bar are measured in hadronic Z events containing prompt muons or electrons, collected by the L3 experiment in the years 1990 to 1995. The total sample of 3.3 milion hadronic Z events with a mean centre-of-mass energy of 91.26 GeV yields: A(FB)(b) = 0.0960 +/- 0.0066(stat.) +/- 0.0033(sys.), chi(b) = 0.1192 +/- 0.0068(stat.)+/- 0.0051(sys.). This asymmetry measurement together with measurements at energies away from the Z pole energy yield a pole asymmetry and corresponding effective electroweak mixing angle of: A(FB)(0,b) = 0.1015 +/- 0.0064(stat.) +/- 0.0035(sys.), sin(theta)(2)W<(theta)over bar> = 0.2318 +/- 0.0013. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

We measure the mass, decay width and production rate of orbitally excited B mesons in 1.25 million hadronic Z decays registered by the L3 detector in 1994 and 1995. B meson candidates are inclusively reconstructed and combined with charged pions produced at the event primary vertex. An excess of events above the expected background is observed in the Bπmass spectrum near 5.7 GeV. These events are interpreted as resulting from the decay B^** -> B^(*)pi, where B^** denotes a mixture of L=1 B meson spin states. The masses and decay widths of the B^*_2 (j_q = 3/2) and B^*_1 (j_q = 1/2) resonances and the relative production rate for the combination of all spin states are extracted from a fit to the mass spectrum.

Measurements of the two-photon interaction e+e− → e+e− + hadrons at s ≃ 91 GeV and s ≃ 183 GeV are presented. The double-tag events, collected with the L3 detector, correspond to interated luminosities of 140 pb−1 at 91 GeV and 52 pb−1 at 183 GeV. The cross-section of γ∗γ∗ collisions has been measured at 〈Q2〉 = 3.5 GeV2 and 〈Q2〉 = 14 GeV2. The data agree well with predictions based on perturbative QCD, while the Quark Parton Model alone is insufficient to describe the data.