A precise determination of the number of families with light neutrinos and of the Z boson partial widths

D. Decamp, B. Deschizeaux, J. P. Lees, M. N. Minard, J. M. Crespo, M. Delfino, E. Fernandez, M. Martinez, R. Miquel, Ll M. Mir, S. Orteu, A. Pacheco, J. A. Perlas, E. Tubau, M. G. Catanesi, M. de Palma, A. Farilla, G. Iaselli, G. Maggi, S. NataliS. Nuzzo, A. Ranieri, G. Raso, F. Romano, F. Ruggieri, G. Selvaggi, L. Silvestris, P. Tempesta, G. Zito, H. Hu, D. Huang, J. Lin, T. Ruan, T. Wang, W. Wu, Y. Xie, D. Xu, R. Xu, J. Zhang, W. Zhao, H. Albrecht, W. B. Atwood, F. Bird, E. Blucher, T. H. Burnett, T. Charity, H. Drevermann, Ll Garrido, C. Grab, R. Hagelberg, S. Haywood, B. Jost, M. Kasemann, G. Kellner, J. Knobloch, A. Lacourt, I. Lehraus, T. Lohse, D. Lüke, A. Marchioro, P. Mato, J. May, A. Minten, A. Miotto, P. Palazzi, M. Pepe-Altarelli, F. Ranjard, A. Roth, J. Rothberg, H. Rotscheidt, W. von Rüden, R. St.Denis, D. Schlatter, M. Takashima, M. Talby, H. Taureg, W. Tejessy, H. Wachsmuth, S. Wheeler, W. Wiedenmann, W. Witzeling, J. Wotschack, Z. Ajaltouni, M. Bardadin-Otwinowska, A. Falvard, P. Gay, P. Henrard, J. Jousset, B. Michel, J. C. Montret, D. Pallin, P. Perret, J. Proriol, F. Prujhière, J. D. Hansen, J. R. Hansen, P. H. Hansen, R. Møllerud, G. Petersen, E. Simopoulou

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Abstract

More extensive and precise results are reported on the parameters of Z decay. On the basis of 20 000 Z decays collected with the ALEPH detector at LEP we find Mz=91.182±0.026 (exp.) ±0.030 (beam) GeV, Γz=2.541±0.056 GeV and σhad0=41.4±0.8 nb. The partial widths for the hadronic and leptonic channels are Γhad=1804±44 MeV, Γe+e-=82.1±3.4 MeV, Γμ+μ-=87.9±6.0 MeV and Γτ+τ-=86.1±5.6 MeV, in good agreement with the standard model. On the basis of the average leptonic width Γℓ+ℓ-=83.9±2.2 MeV, the effective weak mixing angle is found to be sin2θw(Mz)=0.231±0.008. Usin g the partial widths calculated in the standard model, the number of light neutrino families is Nν=3.01±0.15 (exp.)±0.05 (theor.). © 1990.
Original languageEnglish
Pages (from-to)399-411
JournalPhysics Letters B
Volume235
Issue number3-4
DOIs
Publication statusPublished - 1 Feb 1990

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