Title Measurements of the $\tau$-polarisation in $Z^{0}$ decays Author Abreu, P. Boeck, de, H. Brabandere, de, S. Tomaradze, A. Verbeure, F. [et al.] Faculty/Department Faculty of Sciences. Physics Publication type article Publication 1995 Berlin , 1995 Subject Physics Source (journal) Zeitschrift für Physik : C : particles and fields. - Berlin Volume/pages 67(1995) :2 , p. 183-201 ISSN 0170-9739 ISI A1995RJ82200001 Carrier E Target language English (eng) Affiliation University of Antwerp Abstract A sample of Z(0) --> tau(+)tau(-) events observed in the DELPHI detector at LEP in 1991 and 1992 is analysed to measure the tau polarisation in the exclusive decay channels e nu ($) over bar nu, mu nu ($) over bar nu, pi nu, rho nu and a(l) nu. The tau polarisation is also measured with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision than the use of the exclusive decay modes. The results have been combined with those published on the 1990 data. A measurement of the tau polarisation as a function of production angle yields the values for the mean tau polarisation [P-tau] = -0.148 +/- 0.022 and for the Z(0) polarisation P-z = -0.136 +/- 0.027. These results are used to determine the ratio of vector to axial-vector effective couplings for taus ($) over bar upsilon(tau)/($) over bar a(tau) = 0.074 +/- 0.011 and for electrons ($) over bar upsilon(e)/($) over bar a(e) = 0.068 +/- 0.014, compatible with e-tau universality. With the assumption of lepton universality, the ratio of vector to axial-vector effective couplings for leptons ($) over bar upsilon(l)/($) over bar a(l) = 0.072 +/- 0.008 is obtained, implying a value of the effective weak mixing angle sin(2) theta(eff)(lept) = 0.2320 +/- 0.0021. E-info http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1995RJ82200001&DestLinkType=RelatedRecords&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1995RJ82200001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:A1995RJ82200001&DestLinkType=CitingArticles&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 Handle