Showing papers by "J. J. Veillet published in 2000"
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 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: 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: 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 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.
14 citations
10 Jul 2000
5 citations
01 Jan 2000
5 citations
27 Jul 2000
TL;DR: In this article, three analyses are employed to select the taunutaunu, taunucs and cscs final states, and upper limits are set on the production cross section as a function of the branching fraction BR(H+ to tau nu) and of the mass M(H+) under a two-Higgs doublet model.
Abstract: The data collected at centre-of-mass energies of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 176.2 pb-1, are analysed in a search for pair-produced charged Higgs bosons H+/-. Three analyses are employed to select the taunutaunu, taunucs and cscs final states. No evidence for a signal is found. Upper limits are set on the production cross section as a function of the branching fraction BR(H+ to tau nu) and of the mass M(H+), assuming that the sum of the branching ratios is equal to one. In the framework of a two-Higgs-doublet model, charged Higgs bosons with masses below 65.4 GeV/c2 are excluded at 95% confidence level independently of the decay mode.
1 citations