A PRECISE MEASUREMENT OF THE Z RESONANCE PARAMETERS THROUGH ITS HADRONIC DECAYS

A measurement of the cross section for e+e-→ hadrons using 11 000 hadronic decays of the Z boson at ten different center-of-mass energies is presented. A three-parameter fit gives the following values for the Z mass MZ, the total width ΓZ, the product of the electronic and hadronic partial widths ΓeΓh, and the unfolded pole cross section σ0: MZ = 91.171 ± 0.030 (stat.) ± 0.030 (beam) GeV, ΓZ = 2.511 ± 0.065 GeV, ΓeΓh = 0.148 ± 0.006 (stat.) ± 0.004 (syst.) GeV2, σ0 = 41.6 ± 0.7 (stat.) ± 1.1 (syst.) nb, Good agreement with the predictions of the standard model is observed. From a two-parameter fit the number of massless neutrino generations is found to be Nv = 2.91 ± 0.26. Thus the hypothesis of a fourth neutrino with mass less than 40 GeV is excluded with 95% confidence level. Combining the cross section measurements with the ratio Γl/Γh reported in another DELPHI paper [Phys. Lett. B 241 (1990) 425], the hadronic, leptonic and invisible widths are found to be Γh = 1741 ± 61 MeV, Γl = 85.1 ± 2.9 MeV, Γh/Γl = 20.45 ± 0.98, Γinv = 515 ± 54 MeV, in good agreement with the standard model.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Charged particle multiplicity distributions in Z0 hadronic decays

This paper presents an analysis of the multiplicity distributions of charged particles produced in Z0 hadronic decays in the DELPHI detector. It is based on a sample of 25364 events. The average multiplicity is =20.71±0.04(stat)±0.77(syst) and the dispersion D=6.28±0.03(stat)±0.43(syst). The data are compared with the results at lower energies and with the predictions of phenomenological models. The Lund parton shower model describes the data reasonably well. The multiplicity distributions show approximate KNO-scaling. They also show positive forward-backward correlations that are strongest in the central region of rapidity and for particles of opposite charge. © 1991 Springer-Verlag.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Search for pair production of neutral Higgs bosons in Z0 decays

This paper explores a participatory process between a Law lecturer, an academic literacy practitioner and students as teacher agency was conceptualised and theorised as a means of promoting student success. This position paper identifies and advocates a shift in the role of the lecturer as discipline expert to practitioner to provide students with the much needed community of practice (Wenger 1998) and to bridge the gap between epistemological access to disciplines (Morrow 1993) and student identity. This investigation is premised on the notion that students are usually identified as the only ones lacking in effective academic practices; little attention is given to lecturers’ reluctance or inability to embrace methodologies that make disciplinary practices explicit to students to enable them to become academically literate in the discourse of the university as well as their specialist disciplines. The study draws on interviews with the lecturer and focus group discussions with students. Informed by the theories of New Literacy Studies, Rhetorical Studies and Threshold Concepts, the paper presents the notion of ‘crossing the threshold’ from discipline or content expert to discipline practitioner. The paper suggests that it is through intense and sustained critical conversations between the discipline expert, student and academic literacy practitioner that the role of the lecturer may shift to a shared space where academic literacy is embedded in the methodological practices governing the pedagogy of the discipline. It is also suggested that higher education provide the opportunity and scaffolding for lecturers to move into an academic development role within the parameters of their own faculties and disciplines