A precise measurement of the tau polarization and its forward-backward asymmetry at LEP

G Alexander ,R J Hemingway,M Morii,J J Ward,D M Gingrich,D E Plane,P Vikas,J E Pilcher,D Lanske,K Runge,M Steiert,N I Geddes,R Bartoldus,C Markus,A Skillman,E Tsur,A T Watson,U Jost,F G Oakham,P Gagnon,K Stephens,A Gaidot,A Rooke,R D Heuer,F Wäckerle,C R Jones,O Schaile,F Scharf,J Lauber,P Pfeifenschneider,P Poffenberger,M F Turner-Watson,T P Kokott,B W Kennedy,A J Martin,A Jawahery,R Kowalewski,B Stockhausen,P M Watkins,C Charlesworth,R Bürgin,H Mes,S Orito,N K Watson,R J Barlow,T R Junk,A D Schaile,F Strumia,D Chrisman,I J Bloodworth,C Hartmann,P Berlich,F X Gentit,R W Springer,O C Cooke,K W Bell,C K Hargrove,M Hauschild,S Braibant,J Pálinkás,W P Lai,J Ludwig,S R Lautenschlager,H Przysiezniak,D R Ward,M J Goodrick,E A Mckigney,R J Homer,J E Bloomer,P W Jeffreys,D C Imrie,T Behnke,J E Conboy,W R Gibson,M Fierro,I P Duerdoth,T Kawamoto,F Odorici,I Cohen,P Bock,S A Wotton ,G Duckeck,B Nellen,M Gruwé,M Sproston,A K Honma,P Kyberd,D Karlen,J Bechtluft,P Routenburg,M S Dixit,S Söldner-Rembold,G Giacomelli,A Luig,A Posthaus,V Gibson,T Kress,T Tsukamoto,J A Mckenna ,T Hilse,S M Gascon-Shotkin,D E Hutchcroft,W J Mcdonald,A A Carter,J P Pansart,D L Rees,R K Carnegie,C Burgard,R E Hughes-Jones,A Michelini,P Weber,T J Mcmahon,D Axen,H M Bosch,M Thiergen,C Beeston,R Mir,M Starks,C Y Chang,P G Estabrooks,J G Layter,W G Scott,B Wilkens,R Van Kooten ,M J Losty,W Mohr,S D Talbot,H Lafoux,E Lefebvre,H A Neal,N Altekamp,J R Carter,J Goldberg,D R Rust,T Geralis,G P Siroli,R J Hawkings ,C P Ward,J Gascon,G Vasseur,B Poli,M J Oreglia,V Zacek,M Rosvick,D G Fong,Roger Jones ,P Schütz,A S Turcot,F S Merritt,M Tscheulin,J W Gary,P Fath,W Gorn,P Taras,G N Patrick,A M Rossi,M Jimack,A Sittler,J C Hill,M Tecchio,A Joly,G M Dallavalle,J M Roney,K J Anderson,M Hapke,J Steuerer,C M Hawkes,Roberto Giacomelli ,P S Wells,F K Loebinger,R G Kellogg,D Rigby,D Lazic,M Foucher,A M Smith,S A Robins,P Scharff-Hansen,M Jones,P Utzat,K Ametewee,P Mättig,A Fürtjes,G Yekutieli,J P Martin,M Hansroul,B Schmitt ,E Ros ,A Stahl ,V Blobel ,J L Pinfold ,O Biebel ,S Kluth ,C Sbarra ,J Allison ,T Omori ,P A Hart ,H Jérémie ,R Folman ,J Kirk ,R Lahmann ,J S White ,G Bella ,J Hoare ,S Menke ,C Hajdú ,H Burckhart ,L J Levinson ,C H Shepherd-Themistocleous ,P R Hobson ,Martin Ingram ,A M Lee ,J Meyer ,M Cuffiani ,N Wermes ,P Krieger ,A Wagner ,Shinji Yamashita ,Meirin Oan Evans ,S Bentvelsen ,T Włodek ,S Tarem ,Y Rozen ,U Müller ,D S Koetke ,D Strom ,S J Hillier ,S W O’neale ,G Azuelos ,B Bouwens ,H Evans ,R A Mcpherson ,G Pásżtor ,M Schulz ,T Mäshimo ,M Kobel ,H Fukui ,T Mori ,E K.g Sarkisyan ,P Giacomelli ,J R Batley ,T J Smith ,Ch Geich-Gimbel ,D Lellouch ,K Desch ,G Wolf ,E Barberio ,P Jovanović ,S Bethke ,S L Chu ,B J King ,P Capiluppi ,A H Ball ,H.‐C Schultz‐Coulon ,S Dado ,M Verzocchi ,G Herten ,G Mikenberg ,J Von Krogh ,M Thomson ,K Kawagoe ,M G Vincter ,J E.g Edwards ,R Keeler ,H M Fischer ,J Letts ,M Mannelli ,A Malik ,F Fabbri ,H Ogren ,S Schmitt ,M Schröder ,Robert Howard ,R Sobie ,P Schenk ,Ö Runólfsson ,G Hanson ,C Lewis ,Uwe Rüppel ,P Szymański ,T R Wyatt ,J A Wilson ,P Sherwood ,G Beaudoin ,R Nisius ,David Charlton ,R Ryłko ,G W Wilson ,E Duchovni ,T Shears ,S Arcelli ,Tatsuo Kobayashi ,F Fiedler ,M J Pearce ,E Gross ,S J De Jong ,G A Snow ,M Hildreth ,G D Long ,P E.l Clarke ,Shun‐Ichi Tanaka ,P Igo‐Kemenes ,S Komamiya ,S Asai ,R Tafirout ,L A Del Pozo ,S Marcellini ,M Sasaki ,D J Miller ,Eckhard Von Torne ,C Grandi ,J R Pater ,A Mcnab ,F Meijers ,G Jones ,S Anderson ,M Doucet ,S Towers ,A N Bell ,G Martı́nez ,D Horváth ,G Lafferty ,A Skuja ,S L Lloyd ,E Couto E Silva ,N Rodning ,A Montanari ,M Boutemeur,C Dallapiccola,R M Brown,W Matthews,B C Shen,E H Vokurka,S Petzold,B Nijjhar

doi:10.1007/bf02909166

Abstract

A measurement of theτ lepton polarization and its forward-backward asymmetry at the Z0 resonance using the OPAL detector is described. The measurement is based on analyses of τ→ρντ, ττπ(K)ντ, $$\tau \to e\bar \nu _e \nu _\tau $$ , $$\tau \to \mu \bar \nu _\mu \nu _\tau $$ andτ→a1 ν τ decays from a sample of 89075 e+e−→τ + τ − candidates corresponding to an integrated luminosity of 117 pb−1. Assuming that theτ lepton decays according to V-A theory, we measure the averageτ polarization at √s=MZ to be 〈P〉=(−13.0±0.9±0.9)% and theτ polarization forward-backward asymmetry to be A pol FB =(−9.4±1.0±0.4)%, where the first error is statistical and the second systematic. These results are consistent with the hypothesis of lepton universality and, when combined, can be expressed as a measurement of sin2 θ eff lept =0.2334±0.0012 within the context of the Standard Model.

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