15 research outputs found
Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP
Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are
used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~
events. Spin correlations are favoured by data, and found to agree with the
Standard Model predictions. In addition, correlations between the W-boson decay
planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events.
Decay-plane correlations, consistent with zero and with the Standard Model
predictions, are measured
Ultrarelativistic sources in nonlinear electrodynamics
The fields of rapidly moving sources are studied within nonlinear
electrodynamics by boosting the fields of sources at rest. As a consequence of
the ultrarelativistic limit the delta-like electromagnetic shock waves are
found. The character of the field within the shock depends on the theory of
nonlinear electrodynamics considered. In particular, we obtain the field of an
ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure
Measurement of the Cross Section for Open-Beauty Production in Photon-Photon Collisions at LEP
The cross section for open-beauty production in photon-photon collisions is
measured using the whole high-energy and high-luminosity data sample collected
by the L3 detector at LEP. This corresponds to 627/pb of integrated luminosity
for electron-positron centre-of-mass energies from 189GeV to 209GeV. Events
containing b quarks are identified through their semi-leptonic decay into
electrons or muons. The e+e- -> e+e-b b~X cross section is measured within our
fiducial volume and then extrapolated to the full phase space. These results
are found to be in significant excess with respect to Monte Carlo predictions
and next-to-leading order QCD calculations
Measurement of the Z-boson using events at centre-of-mass energies above the Z pole
Events from the e+e- -> Zgamma process with hard initial state radiation collected with the L3 detector at centre-of-mass energies between 183 GeV and 209 GeV are used to measure the mass of the Z boson. Decays of the Z boson into hadrons or muon pairs are considered and the Z mass is determined to be 91.272 +- 0.032 (stat.) +- 0.033 (syst.) GeV, in agreement with the value measured at the Z resonance. Alternatively, assuming this measured value of the Z mass, the method determines the LEP beam energy, found to be 87 +- 34 (stat.) \pm 34 (syst.) MeV lower than the nominal value
Measurement of triple-gauge-boson couplings of the W boson at LEP
The CP-conserving triple-gauge-boson couplings, g(1)(Z), kappa(gamma), lambda(gamma), g(5)(Z), kappa(Z) and lambda(Z) are measured using hadronic and semi-leptonic W-pair events selected in 629 pb(-1) of data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The results are combined with previous L3 measurements based on data collected at lower centre-of-mass energies and with the results from single-W production and from events with a single-photon and missing energy. Imposing the constraints kappa(Z) = g(1)(Z) - tan(2) thetaw(kappa(gamma) - 1) and lambda(Z) = lambda(gamma), we obtain for the C and P conserving couplings the results: g(1)(Z) = 0.966 +/- 0.033(stat) +/- 0.015(syst), kappa(gamma) = 1.013 +/- 0.066(stat) +/- 0.026(syst), lambda(gamma) = -0.021 +/- 0.035(stat) +/- 0.017(syst). Results from the analysis of fully leptonic W-pair decays are also given. All results are in agreement with the Standard Model expectations and confirm the existence of self-couplings among electroweak gauge bosons. (C) 2004 Published by Elsevier B.V