F.L. Linde

Luminosity measurement in the L3 detector at LEP

One of the limiting factors in the determination of the electroweak parameters from cross section measurements of e+e− annihilation close to the Z pole is the precision of the luminosity measurement. The luminosity monitor of the L3 detector at LEP and the analysis of its data are described. Using a combination of a BGO calorimeter and a 3-layer silicon tracker, the absolute luminosity has been measured with an experimental precision of 0.08% in 1993 and 0.05% in 1994. The measurement relies on a detailed understanding of small-angle elastic e+e− (Bhabha) scattering from the experimental and theoretical point of view, as well as an excellent knowledge of the detector geometry.

Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at √sNN = 2.76 TeV with the ATLAS detector

This Letter describes the measurement of √ elliptic flow of charged particles in lead–lead collisions at √sNN = 2.76 TeV using the ATLAS detector at the Large Hadron Collider (LHC). The results are based on an integrated luminosity of approximately 7 μb^(−1). Elliptic flow is measured over a wide region in pseudorapidity, |η| < 2.5, and over a broad range in transverse momentum, 0.5 < p_T < 20 GeV. The elliptic flow parameter v_2 is obtained by correlating individual tracks with the event plane measured using energy deposited in the forward calorimeters. As a function of transverse momentum, v_2(p_T) reaches a maximum at p_T of about 3 GeV, then decreases and becomes weakly dependent on p_T above 7–8 GeV. Over the measured pseudorapidity region, v_2 is found to be only weakly dependent on η, with less variation than observed at lower beam energies. The results are discussed in the context of previous measurements at lower collision energies, as well as recent results from the LHC.

Search for the Standard Model Higgs boson in the decay channel H→ZZ(*)→4ℓ with 4.8 fb-1 of pp collision data at √s=7 TeV with ATLAS

This Letter presents a search for the Standard Model Higgs boson in the decay channel H → ZZ → lll ′+l ′ −, where l, l ′ = e or μ, using proton-proton collisions at √ s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb. The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134−156 GeV, 182−233 GeV, 256−265 GeV and 268−415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125 GeV, 244 GeV and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.

Measurement of the atmospheric muon spectrum from 20 to 3000 GeV

The absolute muon flux between 20 GeV and 300 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 degree to 58 degrees. Due to the large exposure of about 150 m2 sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3% at 150 GeV in the vertical direction is achieved. The ratio of positive to negative muons is studied between 20 GeV and 500 GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003 (stat.)+- 0.019 (syst.).

Single- and multi-photon events with missing energy in e+e - collisions at LEP

Single-and multi-photon events with missing energy are selected in 619 pb −1 of data collected by the L3 detector at LEP at centre-of-mass energies between 189 GeV and 209 GeV. The cross sections of the process e + e − → ν ¯ νγ(γ) are found to be in agreement with the Standard Model expectations, and the number of light neutrino species is determined, including lower energy data, to be N ν = 2.98 ± 0.05 ± 0.04. Selection results are given in the form of tables which can be used to test future models involving single-and multi-photon signatures at LEP. These final states are also predicted by models with large extra dimensions and by several supersymmetric models. No evidence for such models is found. Among others, lower limits between 1.5 TeV and 0.65 TeV are set, at 95% confidence level, on the new scale of gravity for the number of extra dimensions between 2 and 8.

Search for heavy neutral and charged leptons in e+e− annihilation at LEP

A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy leptons are considered. No evidence for their existence is found and lower limits on their masses are set.

Determination of alpha-s from jet multiplicities measured on the Z0 resonance

Whatever the field, major change implies as much as deep transformation of thinking i.e to put in network new skills in particular, those made available by the availability of new technologies. In this context, only one individual cannot join together all necessary skills. It becomes clear that the goal of space valorization cannot be considered without relational investment between the partners and their accumulated background. The local empowerment concerns a collective phenomenon of acquisition and development of skills rests on an learning way appropriate to the potential of the territory to form or promote. The local mediation sets for objective the creation of relations between pre-existent skills and their transfer between the actors, individuals or groups, private or public. But the capacity of the territory to solve these problems will depend closely on the richness of the network and co-operations which it shelters or it will suggest.

Measurement of the inclusive production of neutral pions and charged particles on the Z0 resonance

Abstract We present a study of the inclusive production of neutral pions and charged particles from 112 000 hadronic Z 0 decays. The measured inclusive momentum distributions can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results to e + e − data between √ s = 9 and 91 GeV, we findfind that the evolution of the spectra with center of mass energy is consistent with the QCD predictions.

Search for the direct production of charginos, neutralinos and staus in final states with at least two hadronically decaying taus and missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector

A bstractResults of a search for the electroweak associated production of charginos and next-to-lightest neutralinos, pairs of charginos or pairs of tau sleptons are presented. These processes are characterised by final states with at least two hadronically decaying tau leptons, missing transverse momentum and low jet activity. The analysis is based on an integrated luminosity of 20.3 fb−1 of proton-proton collisions at s=8