Title 



A precise measurement of the polarisation at LEP1
 
Author 



 
Institution/Organisation 



DEPHI Collaboration
 
Abstract 



The tau polarisation has been studied with the e(+)e() > tau(+)tau() data collected by the DELPHI detector at LEP in 1993, 1994 and 1995 around the Z resonance firstly through the exclusive decay channels ev (v) over bar, mu v (v) over bar, pi v, rho v and a(1)v and secondly with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision. The results have been combined with those previously published on 1990 to 1992 DELPHI data, to produce results which reflect the full LEP1 statistics. The fit of the tau polarisation dependence on the production angle yielded the polarisation parameters A(tau) = 0.1359 +/ 0.0096 and A(epsilon) = 0.1382 +/ 0.0116. From these results the ratio of the vector and axialvector effective couplings (v) over bar/(a) over bar(tau) = 0.0683 +/ 0.0048 and (v) over bar/(a) over bar(e) = 0.0694 +/ 0.0058 have been derived, compatible with etau universality. With the assumption of lepton universality, the ratio of vector to axialvector effective couplings for leptons (v) over bar(l)/(a) over bar(l) = 0.0687 +/ 0.0037 was obtained, implying a value of the effective weak mixing angle sin(2) theta(eff)(lept) = 0.23282 +/ 0.00092.   
Language 



English
 
Source (journal) 



European physical journal : C : particles and fields.  Berlin  
Publication 



Berlin : 2000
 
ISSN 



14346044
 
Volume/pages 



14:4(2000), p. 585611
 
ISI 



000088157000002
 
Full text (Publishers DOI) 


  
Full text (publishers version  intranet only) 


  
