436 research outputs found
Real time motion estimation using a neural architecture implemented on GPUs
This work describes a neural network based architecture that represents and estimates object motion in videos. This architecture addresses multiple computer vision tasks such as image segmentation, object representation or characterization, motion analysis and tracking. The use of a neural network architecture allows for the simultaneous estimation of global and local motion and the representation of deformable objects. This architecture also avoids the problem of finding corresponding features while tracking moving objects. Due to the parallel nature of neural networks, the architecture has been implemented on GPUs that allows the system to meet a set of requirements such as: time constraints management, robustness, high processing speed and re-configurability. Experiments are presented that demonstrate the validity of our architecture to solve problems of mobile agents tracking and motion analysis
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 Mass and Width of the W Boson at LEP
We report on measurements of the mass and total decay width of the W boson
with the L3 detector at LEP. W-pair events produced in
interactions between 161 GeV and 183 GeV centre-of-mass energy are selected in
a data sample corresponding to a total luminosity of 76.7 pb. Combining
all final states in W-pair production, the mass and total decay width of the W
boson are determined to be GeV and
GeV, respectively
Search for Heavy Neutral and Charged Leptons in ee Annihilation at = 183 and 189 GeV
A search for unstable neutral and charged heavy leptons as well as for stable
charged heavy leptons is performed at center-of-mass energies = 183
and 189 GeV with the L3 detector at LEP. No evidence for their existence is
found. We exclude neutral heavy leptons which couple to the electron, muon or
tau family, of the Dirac type for masses below 92.4, 93.3 and 83.3 GeV, and of
the Majorana type for masses below 81.8, 84.1 and 73.5 GeV, respectively. We
exclude unstable charged heavy leptons for masses below 93.9 GeV for a wide
range of the associated neutral heavy lepton mass. If the unstable charged
heavy lepton decays to a light neutrino, we exclude masses below 92.4 GeV. The
production of stable charged heavy leptons with mass less than 93.5 GeV is also
excluded
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
Measurement of Exclusive rho+rho- Production in Mid-Virtuality Two-Photon Interactions and Study of the gamma gamma* -> rho rho Process at LEP
Exclusive rho+rho- production in two-photon collisions between a quasi-real
photon, gamma, and a mid-virtuality photon, gamma*, is studied with data
collected at LEP at centre-of-mass energies root(s)=183-209GeV with a total
integrated luminosity of 684.8pb^-1. The cross section of the gamma gamma* ->
rho+ rho- process is determined as a function of the photon virtuality, Q^2,
and the two-photon centre-of-mass energy, W_gg, in the kinematic region:
0.2GeV^2 < Q^2 <0.85GeV^2 and 1.1GeV < W_gg < 3GeV. These results, together
with previous L3 measurements of rho0 rho0 and rho+ rho- production, allow a
study of the gamma gamma* -> rho rho process over the Q^2-region 0.2GeV^2 < Q^2
< 30 GeV^2
Search for Anomalous Couplings in the Higgs Sector at LEP
Anomalous couplings of the Higgs boson are searched for through the processes
e^+ e^- -> H gamma, e^+ e^- -> e^+ e^- H and e^+ e^- -> HZ. The mass range 70
GeV < m_H < 190 GeV is explored using 602 pb^-1 of integrated luminosity
collected with the L3 detector at LEP at centre-of-mass energies
sqrt(s)=189-209 GeV. The Higgs decay channels H -> ffbar, H -> gamma gamma, H
-> Z\gamma and H -> WW^(*) are considered and no evidence is found for
anomalous Higgs production or decay. Limits on the anomalous couplings d, db,
Delta(g1z), Delta(kappa_gamma) and xi^2 are derived as well as limits on the H
-> gamma gamma and H -> Z gamma decay rates
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 the Running of the Electromagnetic Coupling at Large Momentum-Transfer at LEP
The evolution of the electromagnetic coupling, alpha, in the
momentum-transfer range 1800GeV^2 < -Q^2 < 21600GeV^2 is studied with about
40000 Bhabha-scattering events collected with the L3 detector at LEP at
centre-of-mass energies 189-209GeV. The running of alpha is parametrised as:
alpha(Q^2) = alpha_0/(1-C Delta alpha(Q^2)), where alpha_0=\alpha(Q^2=0) is the
fine-structure constant and C=1 corresponds to the evolution expected in QED. A
fit to the differential cross section of the e+e- ->e+e- process for scattering
angles in the range |cos theta|<0.9 excludes the hypothesis of a constant value
of alpha, C=0, and validates the QED prediction with the result: C = 1.05 +/-
0.07 +/- 0.14, where the first uncertainty is statistical and the second
systematic
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
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