Analysis of the decayτ- →π-π-π+vτ and determination of thea1(1260) resonance parameters

Autor: Albrecht, H., Ehrlichmann, H., Hamacher, T., Hofmann, R. P., Kirchhoff, T., Nau, A., Nowak, S., Schröder, H., Schulz, H. D., Walter, M., Wurth, R., Appuhn, R. D., Hast, C., Kolanoski, H., Lange, A., Lindner, A., Mankel, R., Schieber, M., Siegmund, T., Spaan, B., Thurn, H., Töpfer, D., Walther, A., Wegener, D., Bittner, M., Eckstein, P., Paulini, M., Reim, K., Wegener, H., Mundt, R., Oest, T., Reimer, R., Schmidt-Parzefall, W., Funk, W., Stiewe, J., Werner, S., Ehret, K., Hofmann, W., Hüpper, A., Khan, S., 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., Prentice, J. D., Saull, P. R. B., Tzamariudaki, K., Van de Water, R. G., Yoon, T. -S., Reßing, D., Schmidtler, M., Schneider, M., Schubert, K. R., Strahl, K., Waldi, R., Weseler, S., Kernel, G., Križan, P., Križnič, E., Podobnik, T., Živko, T., Balagura, V., Belyaev, I., Chechelnitsky, S., Danilov, M., Droutskoy, A., Gershtein, Yu., Golutvin, A., Gorelov, I., Kostina, G., Lubimov, V., Pakhlov, P., Ratnikov, F., Semenov, S., Shibaev, V., Soloshenko, V., Tichomirov, I., Zaitsev, Yu.
Zdroj: Zeitschrift für Physik C Particles and Fields; March 1993, Vol. 58 Issue: 1 p61-70, 10p
Abstrakt: Using the ARGUS detector at the DORIS IIe+e− storage ring we have studied the three-pion hadronic final state in the decay τ- → π-π-π+vτ. From about 7500 events we conclude that the three-pion system is dominated by theJP=1+ resonancea1 (1260) decaying preferentially via ρ0π-. 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 yields $$m_{a_1 } = (1.211 \pm 0.007 \pm _{0.0}^{0.050} ) GeV/c^2 $$ and $$\Gamma _{a_1 } = (0.446 \pm 0.0021 \pm _{0.0}^{0.140} ) GeV/c^2 $$ . The second errors reflect the model dependence of the result. This is the currently most significant determination of thea1 resonance parameters. The ratio ofS- andD-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 parameter $$\gamma _{AV} = 2g_A g_V /(g_A^2 + g_V^2 )$$ to 1.25±0.23±0.080.15. The branching ratio of the decay τ- → π-π-π+vτ is determined to be Br(τ- → π-π-π+vτ)=(6.8±0.1±0.5)%.
Databáze: Supplemental Index
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