Measurement of the ZZ cross-section in e+e- interactions at 183-189 GeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 497:3-4 (2001) 199-213
Abstract:
Measurements of on-shell ZZ production are described, using data collected by DELPHI in 1997 and 1998, at centre-of-mass energies √s = 182.6 GeV and 188.6 GeV, respectively. Results obtained in each of the final states qq̄qq̄, μ+μ-qq̄, e+e-qq̄, vv̄qq̄ l+l-l+l-, and vv̄l+l- are presented. The measured cross-sections for on-shell ZZ production via the tree-level doubly-resonant graphs (NC02) are: σNC02 (182.6 GeV) = 0.38 ± 0.18 (stat) ± 0.04 (syst) pb, σNC02 (188.6 GeV) = 0.60±0.13 (stat) ±0.07 (syst) pb. They are consistent with the Standard Model expectations of 0.25 and 0.65 pb at each energy. © 2001 Elsevier Science B.V.A measurement of the Tau topological branching ratios
European Physical Journal C 20:4 (2001) 617-637
Abstract:
Using data collected in the DELPHI detector at LEP-1, measurements of the inclusive τ branching ratios for decay modes containing one, three, or five charged particles have been performed, giving the following results: B1 ≡ B(τ- → (particle)-≥0π0≥0K0 vτ(v̄)) = (85.316 ± 0.093 ± 0.049)%; B3 ≡ B(τ- → 2h-h+≥0π0≥0K0vτ) = (14.569 ± 0.093 ± 0.048)%; B5 ≡ B(τ- → 3h-2h+≥0π0≥0K0vτ) = (0.115 ± 0.013 ± 0.006)%, where h is either a charged π or K meson. The first quoted uncertainties are statistical and the second systematic.Measurement of the semileptonic b branching fractions and average b mixing parameter in Z decays
European Physical Journal C 20:3 (2001) 455-478
Abstract:
The semileptonic branching fractions for primary and cascade b decays BR(b → l-), BR(b → c → l+) and BR(b → c̄ → l- were measured in hadronic Z decays collected by the DELPHI experiment at LEP. The sample was enriched in b decays using the lifetime information and various techniques were used to separate leptons from direct or cascade b decays. By fitting the momentum spectra of di-leptons in opposite jets, the average b mixing parameter x̄ was also extracted. The following results have been obtained: (equation presented).Search for neutralino pair production at √s = 189 GeV
European Physical Journal C 19:2 (2001) 201-212
Abstract:
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV gave no evidence for a signal. This limits the neutralino production cross-section and excludes regions in the parameter space of the Minimal Supersymmetric Standard Model (MSSM).Search for sleptons in e+e- collisions at √s = 183 to 189 GeV
European Physical Journal C 19:1 (2001) 29-42