We acknowledge in particular the support of Austrian Federal Ministry of Education, Science and Culture, GZ 616.364/2-III/2a/98, FNRS–FWO, Flanders Institute to encourage scientific and technological research in the industry (IWT), Belgium, FINEP, CNPq, CAPES, FUJB and FAPERJ, Brazil, Czech Ministry of Industry and Trade, GA CR 202/99/1362, Commission of the European Communities (DG XII), Direction des Sciences de la Matiere, CEA, France, Bundesministerium fur Bildung, Wissenschaft, Forschung und Technologie, Germany, General Secretariat for Research and Technology, Greece, National Science Foundation (NWO) and Foundation for Research on Matter (FOM), The Netherlands, Norwegian Research Council, State Committee for Scientific Research, Poland, SPUB-M/CERN/PO3/DZ296/2000, SPUB-M/CERN/PO3/DZ297/2000, 2P03B 104 19 and 2P03B 69 23(2002-2004) FCT- Fundaçao para a Ciencia e Tecnologia, Portugal, Vedecka grantova agentura MS SR, Slovakia, Nr. 95/5195/134, Ministry of Science and Technology of the Republic of Slovenia, CICYT, Spain, AEN99-0950 and AEN99-0761, The Swedish Natural Science Research Council, Particle Physics and Astronomy Research Council, UK, Department of Energy, USA, DE-FG02-01ER41155. EEC RTN contract HPRN-CT-00292-2002.

The tau lepton lifetime has been measured with the e+e− → τ+τ− events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong τ decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave ττ(1 prong) = 291.8 ± 2.3stat ± 1.5sys fs. A third measurement using taus which decayed to three charged particles yielded ττ(3 prong) = 288.6 ± 2.4stat ± 1.3sys fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be ττ = 290.9 ±1.4stat ± 1.0sys fs.

DELPHI Collaboration: et al.

arXiv:hep-ex/0410010v1

CERN–EP/2003-070

Peer reviewed