155 research outputs found
Neutral-Current Four-Fermion Production in e+e- Interactions at LEP
Neutral-current four-fermion production, e+e- -> ffff is studied in 0.7/fb of
data collected with the L3 detector at LEP at centre-of-mass energies
root(s)=183-209GeV. Four final states are considered: qqvv, qqll, llll and
llvv, where l denotes either an electron or a muon. Their cross sections are
measured and found to agree with the Standard Model predictions. In addition,
the e+e- -> Zgamma* -> ffff process is studied and its total cross section at
the average centre-of-mass energy 196.6GeV is found to be 0.29 +/- 0.05 +/-
0.03 pb, where the first uncertainty is statistical and the second systematic,
in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass
spectra of the qqll final states are analysed to search for the possible
production of a new neutral heavy particle, for which no evidence is found
Z Boson Pair-Production at LEP
Events stemming from the pair-production of Z bosons in e^+e^- collisions are
studied using 217.4 pb^-1 of data collected with the L3 detector at
centre-of-mass energies from 200 GeV up to 209 GeV. The special case of events
with b quarks is also investigated.
Combining these events with those collected at lower centre-of-mass energies,
the Standard Model predictions for the production mechanism are verified. In
addition, limits are set on anomalous couplings of neutral gauge bosons and on
effects of extra space dimensions
Study of the e+e- -> Ze+e- process at LEP
The cross section of the process e+e- -> Ze+e is measured with 0.7fb^-1 of
data collected with the L3 detector at LEP. Decays of the Z boson into quarks
and muons are considered at centre-of-mass energies ranging from 183GeV up to
209GeV. The measurements are found to agree with Standard Model predictions,
achieving a precision of about 10% for the hadronic channel
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 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
Production of Single W Bosons at LEP and Measurement of WWgamma Gauge Coupling Parameters
Single W boson production in electron-positron collisions is studied with the
L3 detector at centre-of-mass energies between 192 GeV and 209 GeV. Events with
two acoplanar hadronic jets or a single energetic lepton are selected, and the
single W cross section is measured. Combining the results with measurements at
lower centre-of-mass energies, the ratio of the measured cross section to the
Standard Model expectation is found to be 1.12^{+0.11}_{-0.10}+/-0.03. From all
single W data, the WWgamma gauge coupling parameter kappa_gamma is measured to
be 1.116^{+0.082}_{-0.086}+/-0.068
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