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Search for colour reconnection effects in e+e- -> W+W- -> hadrons through particle-flow studies at LEP
(2003)Physics Letters BA search for colour reconnection effects in hadronic decays of W pairs is performed with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The analysis is based on the study of the particle flow between jets associated to the sameW boson and between two different W bosons in qqqq events. The ratio of particle yields in the different interjet regions is found to be sensitive to colour reconnection effects implemented in ...Journal Article -
Measurement of the atmospheric muon spectrum from 20 to 3000 GeV
(2004)Physics Letters BThe absolute muon flux between 20 and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0°to 58°. Due to the large exposure of about 150 m2sr 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 and 500 GeV, and the average vertical muon charge ratio is ...Journal Article -
Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP
(2005)Physics Letters BThe evolution of the electromagnetic coupling, α, in the momentum-transfer range 1800 GeV2 < -Q2 < 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies √s = 189-209 GeV. The running of α is parametrised as: α(Q2) = α0/1 - C Δα(Q2), where α ≡ α(Q2 = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential ...Journal Article -
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Z boson pair-production at LEP
(2003)Physics Letters BEvents 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 ...Journal Article -
A measurement of the gluon splitting rate into c(c)over-bar pairs in hadronic Z decays
(2003)Physics Letters BThe rate of gluon splitting into c ̄c pairs in hadronic Z decays is measured using the data sample collected by ALEPH from 1991 to 1995. The selection is based on the identification of leptons (electrons and muons) originating from semileptonic charm decays, and on the topological properties of signal events. The result derived from the selected sample is gc ̄c = (3.26 ± 0.23(stat) ± 0.42(syst))%.Journal Article -
Production properties of K*(892)± vector mesons and their spin alignment as measured in the NOMAD experiment
(2006)The European Physical Journal CFirst measurements of K⋆(892)± mesons production properties and their spin alignment in νμ charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For K⋆+ and K⋆− mesons produced in νμ CC interactions and decaying into K0π± we have found the following yields per event: (2.6±0.2(stat.)±0.2(syst.))% and (1.6±0.1(stat ...Journal Article -
Search for Higgs bosons decaying to WW in e+e- collisions at LEP
(2007)The European Physical Journal CA search for Higgs bosons produced in association with a fermion pair, and decaying to WW, is performed with the data collected by the ALEPH detector at centre-of-mass energies ranging from 191 to 209 GeV. The data correspond to an integrated luminosity of 453.2 pb-1. Thirteen exclusive selections are developed according to the different final state topologies. No statistically significant evidence for a Higgs boson decaying into a WW ...Journal Article -
Search for single top quark production in ep collisions at HERA
(2004)The European Physical Journal CA search for single top quark production is performed in e±p collisions at HERA. The search exploits data corresponding to an integrated luminosity of 118.3 pb-1. A model for the anomalous production of top quarks in a flavour changing neutral current process involving a tuγ coupling is investigated. Decays of top quarks into a b quark and a W boson are considered in the leptonic and the hadronic decay channels of the W. Both a cut-based ...Journal Article -
Measurement of beauty production at HERA using events with muons and jets
(2005)The European Physical Journal CA measurement of the beauty production cross section in ep collisions at a centre-of-mass energy of 319 GeV is presented. The data were collected with the H1 detector at the HERA collider in the years 1999-2000. Events are selected by requiring the presence of jets and muons in the final state. Both the long lifetime and the large mass of b-flavoured hadrons are exploited to identify events containing beauty quarks. Differential cross ...Journal Article