Author/Authors :
H. Albrecht، نويسنده , , T. Hamacher، نويسنده , , R.P. Hofmann، نويسنده , , Karin T. Kirchhoff، نويسنده , , R. Mankel، نويسنده , , A. Nau، نويسنده , , S. Nowak، نويسنده , , D. Re?ing، نويسنده , , H. Schr?der، نويسنده , , H.D. Schulz، نويسنده , , M. Walter، نويسنده , , R. Wurth، نويسنده , , C. Hast، نويسنده , , H. Kapitza، نويسنده , , H. Kolanoski، نويسنده , , A. Kosche، نويسنده , , A. Lange، نويسنده , , A. Lindner، نويسنده , , M. Schieber، نويسنده , , T. Siegmund، نويسنده , , et al.، نويسنده ,
Abstract :
Using the ARGUS detector at the e+e− storage ring DORIS II, we have determined the Michel parameters ξ and δ of τ∓ → l∓νν- decays. With an integrated luminosity of 445 pb−1 around s= 10GeV, we have produced approximately 415000 τ-pairs. From this data sample, 3262 events were selected with e+e− → τ+τ− → (l±νν-) (π∓π+π−ν). The semihadronic decay was used as analyser of the τ-spin and made possible - owing to the spin correlations - the determination of the parity-violating Michel parameters ξ and δ in the decay τ∓ → l∓νν-. Simultaneously to the determination of the Michel parameters, a measurement of the τ-neutrino helicity hντ in the decay τ∓ → π∓π+π−ν was obtained. We observed hντ = −0.85−0.17+0.15 ± 0.05, ϱ = 0.721 ± 0.040 ± 0.021, ξ = 1.26−0.26+0.30 ± 0.09, and ξδ = 0.77−0.16+0.18 ± 0.05. In addition, the combined ARGUS result on hντ, ϱ, ξ, and ξδ are reported using this work and previous measurements.
