1. Analysis of the decay $\tau^- \to \pi^-\pi^- \pi^+v_\tau$ and determination of thea 1(1260) resonance parameters
- Author
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Albrecht, H., Ehrlichmann, H., Wurth, R., Appuhn, R. D., Hast, C., Kolanoski, H., Lange, A., Lindner, A., Mankel, R., Schieber, M., Siegmund, T., Spaan, B., Hamacher, T., Thurn, H., Töpfer, D., Walther, A., Wegener, D., Bittner, M., Eckstein, P., Paulini, M., Reim, K., Wegener, H., Mundt, R., Hofmann, R. P., Oest, T., Reimer, R., Schmidt-Parzefall, W., Funk, W., Stiewe, J., Werner, S., Ehret, K., Hofmann, W., Hüpper, A., Khan, S., Kirchhoff, T., Knöpfle, K. T., Spengler, J., Britton, D. I., Charlesworth, C. E. K., Edwards, K. W., Hyatt, E. R. F., Kapitza, H., Krieger, P., MacFarlane, D. B., Patel, P. M., Nau, A., Prentice, J. D., Saull, P. R. B., Tzamariudaki, K., Water, R. G., Yoon, T. -S., Reßing, D., Schmidtler, M., Schneider, M., Schubert, K. R., Strahl, K., Nowak, S., Waldi, R., Weseler, S., Kernel, G., Križan, P., Križnič, E., Podobnik, T., Živko, T., Balagura, V., Belyaev, I., Chechelnitsky, S., Schröder, H., Danilov, M., Droutskoy, A., Gershtein, Yu., Golutvin, A., Gorelov, I., Kostina, G., Lubimov, V., Pakhlov, P., Ratnikov, F., Semenov, S., Schulz, H. D., Shibaev, V., Soloshenko, V., Tichomirov, I., Zaitsev, Yu., ARGUS Collaboration, and Walter, M.
- Subjects
annihilation: electron positron ,electroproduction: tau ,ARGUS ,Dalitz plot ,semileptonic decay: tau ,annihilation [electron positron] ,M010DS ,tau- [semileptonic decay] ,mass spectrum: ((n)pi) ,a1(1260): width ,a1(1260) [hadronic decay] ,electroproduction [tau] ,+pi%2B+2pi-+neutrino%2Ftau%22">tau- --> pi+ 2pi- neutrino/tau ,mass [a1(1260)] ,electron positron [colliding beams] ,+rho%28770%290+pi%22">a1(1260) --> rho(770)0 pi ,decay: asymmetry ,a1(1260): mass ,a1(1260) [mass] ,tau: pair production ,hadronic decay: a1(1260) ,tau [pair production] ,electron positron: colliding beams ,asymmetry: decay ,tau [electroproduction] ,9.4-10.6 GeV-cms ,+a1%281260%29+neutrino%2Ftau%22">tau- --> a1(1260) neutrino/tau ,pair production [tau] ,asymmetry [decay] ,width [a1(1260)] ,colliding beams [electron positron] ,a1(1260): hadronic decay ,semileptonic decay [tau-] ,tau-: branching ratio ,M010M ,DESY DORIS Stor ,partial wave ,S035XA1 ,mass: a1(1260) ,electron positron: annihilation ,M010W ,((n)pi): mass spectrum ,parity: violation ,S035XAL ,pair production: tau ,ddc:530 ,decay [asymmetry] ,parity [violation] ,tau-: semileptonic decay ,electron positron [annihilation] ,violation: parity ,hadronic decay [a1(1260)] ,branching ratio [tau-] ,((n)pi) [mass spectrum] ,mass spectrum [((n)pi)] ,colliding beams: electron positron ,tau: electroproduction ,violation [parity] ,experimental results - Abstract
22 pp. (1993)., Using the ARGUS detector at the DORIS II $e^+e^−$ storage ring we have studied the three-pion hadronic final state in the decay $τ^- → π^-π^-π^+v_τ$. From about 7500 events we conclude that the three-pion system is dominated by the $J^P=1^+$ resonancea1 (1260) decaying preferentially via $ρ^0π^-$. Our data restrict a possible ρπ contribution of three-pion states without intermediate resonances to less than 6% at 95% CL. Fitting a model by Isgur et al. to the data yieldsma1=(1.211±0.007±0.0500.0)GeV/c$^2$ and $Γ$a1=(0.446±0.0021±0.1400.0)GeV/c$^2$. The second errors reflect the model dependence of the result. This is the currently most significant determination of thea1 resonance parameters. The ratio ofS- and D-wave amplitudes for the ρ0π- intermediate state of thea1− decay at the nominala1− mass was found to beD/S=−0.11±0.02. Using thisD/S ratio we update our former measurement of the parity violating asymmetry parameterγ $AV=2gAgV/(g^2_A+g^2_V)$ to 1.25±0.23±0.080.15. The branching ratio of the decay $τ^- → π^-π^-π^+v_τ$ is determined to be Br($τ^- → π^-π^-π^+v_τ$)=(6.8±0.1±0.5)%.
- Published
- 1993
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