Hadronic structure in the decay τ-→ντπ-π 0π0 and the sign of the tau neutrino helicity Article

Asner, DM, Eppich, A, Gronberg, J et al. (2000). Hadronic structure in the decay τ-→ντπ-π 0π0 and the sign of the tau neutrino helicity . PHYSICAL REVIEW D, 61(1), 1-22. 10.1103/PhysRevD.61.012002

cited authors

  • Asner, DM; Eppich, A; Gronberg, J; Hill, TS; Lange, DJ; Morrison, RJ; Nelson, HN; Nelson, TK; Roberts, D; Behrens, BH; Ford, WT; Gritsan, A; Krieg, H; Roy, J; Smith, JG; Alexander, JP; Baker, R; Bebek, C; Berger, BE; Berkelman, K; Boisvert, V; Cassel, DG; Crowcroft, DS; Dickson, M; Von Dombrowski, S; Drell, PS; Ecklund, KM; Ehrlich, R; Foland, AD; Gaidarev, P; Galik, RS; Gibbons, L; Gittelman, B; Gray, SW; Hartill, DL; Heltsley, BK; Hopman, PI; Kreinick, DL; Lee, T; Liu, Y; Meyer, TO; Mistry, NB; Ng, CR; Nordberg, E; Ogg, M; Patterson, JR; Peterson, D; Riley, D; Soffer, A; Thayer, JG; Thies, PG; Valant-Spaight, B; Warburton, A; Ward, C; Athanas, M; Avery, P; Jones, CD; Lohner, M; Prescot, C; Rubiera, AI; Yelton, J; Zheng, J; Brandenburg, G; Briere, RA; Ershov, A; Gao, YS; Kim, DYJ; Wilson, R; Browder, TE; Li, Y; Rodriguez, JL; Yamamoto, H; Bergfeld, T; Eisenstein, BI; Ernst, J; Gladding, GE; Gollin, GD; Hans, RM; Johnson, E; Karliner, I; Marsh, MA; Palmer, M; Plager, C; Sedlack, C; Selen, M; Thaler, JI; Williams, J; Edwards, KW; Bellerive, A; Janicek, R; Patel, PM; Sadoff, AJ; Ammar, R; Baringer, P; Bean, A; Besson, D; Coppage, D; Davis, R; Kotov, S; Kravchenko, I

authors

abstract

  • Based on a sample corresponding to 4.3×106 produced τ-pair events, we have studied hadronic dynamics in the decay τ-→ντπ-π 0π0 in data recorded by the CLEO II detector operating at the CESR e+e- collider. The decay is dominated by the process τ-→ντa1-(1260), with the a1- meson decaying to three pions predominantly via the lowest dimensional (mainly S-wave) ρ-π0 Born amplitude. From model-dependent fits to the Dalitz plot and angular observables in bins of 3 π mass, we find significant additional contributions from amplitudes for a1 decay to σπ, f0(1370)π, and f2(1270)π, as well as higher dimensional a1→ρπ and ρ′ π amplitudes. Notably, the squared σπ amplitude accounts for approximately 15% of the total τ- →ντπ-π0π0 rate in the models considered. The data are well described using couplings to these amplitudes that are independent of the 3π mass. These amplitudes also provide a good description for the τ- →ντπ-π0π0 Dalitz plot distributions. We have searched for additional contributions from τ-→ντπ′ -(1300). We place 90% confidence level upper limits on the branching fraction for this channel of between 1.0×10-4 and 1.9×10-4, depending on the π′ decay mode considered. The π-π0π0 mass spectrum is parametrized by a Breit-Wigner form with a mass-dependent width which is specified according to the results of the Dalitz plot fits plus an unknown coupling to an a1→K*K amplitude. From a χ2 fit using this parametrization, we extract the pole mass and width of the a1, as well as the magnitude of the K*K coupling. We have also investigated the impact of a possible contribution from the a1′(1700) meson on this spectrum. Finally, exploiting the parity-violating angular asymmetry in a1→3π decay, we determine the signed value of the τ neutrino helicity to be hντ=-1.02±0.13 (stat)±0.03 (syst+model), confirming the left-handedness of the τ neutrino. ©1999 The American Physical Society.

publication date

  • January 1, 2000

published in

Digital Object Identifier (DOI)

start page

  • 1

end page

  • 22

volume

  • 61

issue

  • 1