Showing papers by "Werner Wiedenmann published in 2000"
TL;DR: In this article, a search for the Standard Model Higgs boson in the data sample collected with the ALEPH detector at LEP, at centre-of-mass energies up to 209 GeV, was performed.
157 citations
TL;DR: In this article, a search for charged Higgs bosons produced in pairs is performed with data collected at centre-of-mass energies ranging from 189 to 209 GeV by ALEPH at LEP, corresponding to a total luminosity of 629 invpb.
86 citations
TL;DR: In this article, an experimental investigation of the structure of identified quark and gluon jets is presented; this allows for tests of QCD over a wide range of transverse momentum scales.
Abstract: An experimental investigation of the structure of identified quark and gluon jets is presented. Observables related to both the global and internal structure of jets are measured; this allows for tests of QCD over a wide range of transverse momentum scales. The observables include distributions of jet-shape variables, the mean and standard deviation of the subjet multiplicity distribution and the fragmentation function for charged particles. The data are compared with predictions of perturbative QCD as well as QCD-based Monte Carlo models. In certain kinematic regions the measurements are sensitive mainly to perturbatively calculable effects, allowing for a test of QCD. The comparisons are also extended into regions where nonperturbative effects become large, and in this way the transition from hard to soft QCD is investigated. It is found that by including leading and next-to-leading logarithmic contributions in the QCD predictions, the agreement with the data can be extended to lower transverse momentum scales, especially for gluon jets.
40 citations
TL;DR: In this article, the authors used the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays and selected 23 candidates with an estimated purity of 71%.
38 citations
TL;DR: In this article, the mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects, and the measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.
Abstract: Hadronic Z decay data taken with the ALEPH detector at LEP1 are used to measure the three-jet rate as well as moments of various event-shape variables. The ratios of the observables obtained from b-tagged events and from an inclusive sample are determined. The mass of the b quark is extracted from a fit to the measured ratios using a next-to-leading order prediction including mass effects. Taking the first moment of the $y_3$
distribution, which is the observable with the smallest hadronization corrections and systematic uncertainties, the result is
\[m_b(M_{\mathrm Z}) = \left[3.27 \pm 0.22 (\mathrm{stat}) \pm 0.22 (\mathrm{exp}) \pm 0.38 (\mathrm{had}) \pm 0.16 (\mathrm{theo})\right] \;\gevcc\quad. \] The measured ratio is alternatively employed to test the flavour independence of the strong coupling constant for b and light quarks.
30 citations
TL;DR: The Instituto de Fisica Teorica Universidade Estadual Paulista, Rua Pamplona 145, 01405-900, Sao Paulo, Brazil as discussed by the authors.
29 citations
TL;DR: In this paper, the ALEPH detector at LEP1 has been used to search for γγ production of the glueball candidates f0(1500) and fJ(1710) via their decay to π+π−.
28 citations
TL;DR: Two-particle correlations of Lambda Lambda and pairs have been studied in multihadronic Z decays recorded with the ALEPH detector at LEP in the years from 1992 to 1995 as discussed by the authors.
26 citations
TL;DR: In this paper, the decay of hadronic Z decays recorded with the ALEPH detector from 1991 to 1995 is observed, based on tagging the final state with two φ mesons in the same hemisphere.
21 citations
TL;DR: In this paper, the authors measured the decay branching fraction of the W boson into hadrons at lower center-of-mass energies and showed that B(W → hadrons) = 66.97 ± 0.65(stat.) ± 0.32(syst.)%, allowing a determination of the CKM matrix element |Vcs| = 0.951 ± 0.,
18 citations
TL;DR: In this article, a scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime.
Abstract: Searches for topologies characteristic of Gauge Mediated SUSY Breaking models (GMSB) are performed by analysing 173.6 pb^-1 of data collected at Ecm = 188.6~GeV with the ALEPH detector.These topologies include acoplanar photons, non-pointing single photon, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and four leptons plus missing energy final states.No evidence for these new phenomena is observed and limits on production cross sections and sparticle masses are derived. A scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime.
TL;DR: In this paper, the ALEPH detector at LEP collected at center-of-mass energies from 189 GeV to 202 GeV, corresponding to an integrated luminosity of 411 pb-1, are analysed in a search for the scalar top in the decay channels'stop -> c/u neutralino' for small mass differences between the stop and the lightest neutralino.
TL;DR: In this paper, a search for gamma-gamma decays of a Higgs boson is performed in the data sample collected at LEP with the ALEPH detector between 1991 and 1999.
TL;DR: In this article, single top production via flavour changing neutral currents in the reactions e + e − → t c / u is searched for in approximately 411 −pb −1 of data collected by ALEPH at center-of-mass energies in the range between 189 and 202 −GeV.