100 research outputs found
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
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
Search for a Higgs Boson Decaying to Weak Boson Pairs at LEP
A Higgs particle produced in association with a Z boson and decaying into
weak boson pairs is searched for in 336.4 1/pb of data collected by the L3
experiment at LEP at centre-of-mass energies from 200 to 209 GeV. Limits on the
branching fraction of the Higgs boson decay into two weak bosons as a function
of the Higgs mass are derived. These results are combined with the L3 search
for a Higgs boson decaying to photon pairs. A Higgs produced with a Standard
Model e+e- --> Zh cross section and decaying only into electroweak boson pairs
is excluded at 95% CL for a mass below 107 GeV
Lambda and Sigma0 Pair Production in Two-Photon Collisions at LEP
Strange baryon pair production in two-photon collisions is studied with the
L3 detector at LEP. The analysis is based on data collected at e+e-
centre-of-mass energies from 91 GeV to 208 GeV, corresponding to an integrated
luminosity of 844 pb-1. The processes gamma gamma -> Lambda Anti-lambda and
gamma gamma -> Sigma0 Anti-sigma0 are identified. Their cross sections as a
function of the gamma gamma centre-of-mass energy are measured and results are
compared to predictions of the quark-diquark model
Inclusive Charged Hadron Production in Two-Photon Collisions at LEP
Inclusive charged hadron production, e+e- -> e+e- h+- X, is studied using 414
pb-1 of data collected at LEP with the L3 detector at centre-of-mass energies
between 189 and 202 GeV. Single particle inclusive differential cross sections
are measured as a function of the particle transverse momentum, pt, and
pseudo-rapidity, eta. For p_t < 1.5 GeV, the data are well described by an
exponential, typical of soft hadronic processes. For higher pt, the onset of
perturbative QCD processes is observed. The pi+- production cross section for
pt > 5 GeV is much higher than the NLO QCD predictions
Bose-Einstein Correlations of Neutral and Charged Pions in Hadronic Z Decays
Bose-Einstein correlations of both neutral and like-sign charged pion pairs
are measured in a sample of 2 million hadronic Z decays collected with the L3
detector at LEP. The analysis is performed in the four-momentum difference
range 300 MeV < Q < 2 GeV. The radius of the neutral pion source is found to be
smaller than that of charged pions. This result is in qualitative agreement
with the string fragmentation model
The e+e- -> Z gamma gamma -> q q gamma gamma Reaction at LEP and Constraints on Anomalous Quartic Gauge Boson Couplings
The cross section of the process e^+ e^- -> Z \gamma\gamma -> qq \gamma
\gamma is measured with 215 pb^-1 of data collected with the L3 detector during
the final LEP run at centre-of-mass energies around 205 GeV and 207 GeV. No
deviation from the Standard Model expectation is observed. The full data sample
of 713 pb^-1, collected above the Z resonance, is used to constrain the
coefficients of anomalous quartic gauge boson couplings to:
-0.02 GeV^-2 < a_0/\Lambda^2 < 0.03 GeV^-2 and -0.07 GeV^-2 < a_c/\Lambda^2 <
0.05 GeV^-2, at 95% confidence level
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at sqrt(s) up to 209 GeV
A search for the lightest neutral CP-even and neutral CP-odd Higgs bosons of
the Minimal Supersymmetric Standard Model is performed using 216.6 pb-1 of data
collected with the L3 detector at LEP at centre-of-mass energies between 203
and 209 GeV. No indication of a signal is found. Including our results from
lower centre-of-mass energies, lower limits on the Higgs boson masses are set
as a function of tan(beta) for several scenarios. For tan(beta) greater than
0.7 they are mh > 84.5 GeV and mA > 86.3 GeV at 95% confidence level
Measurement of charged-particle multiplicity distributions and their H_q moments in hadronic Z decays at LEP
The charged-particle multiplicity distribution is measured for all hadronic
events as well as for light-quark and b-quark events produced in e+e-
collisions at the Z pole. Moments of the charged-particle multiplicity
distributions are calculated. The H moments of the multiplicity distributions
are studied, and their quasi-oscillations as a function of the rank of the
moment are investigated.Comment: Matches published versio
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