Abstract

The Crystal Ball detector at the DORIS II storage ring at DESY has been used to measure the branching ratios for the decay modes τ ±→h ± π 0 ν and τ ±→h ± π 0 π 0 ν, where h ± is any charged hadron. The results are BR( τ ±→ h ± π 0 ν) = (22.0±0.8±1.9)%, BR( τ ±→ h ± π 0 π 0 ν) = (5.7±0.5 +1.0 −1.7)%. The first result is in good agreement with the present world average. The decay mode h ± π 0 π 0 ν is reconstructed in τ decays for the first time. Its branching ratio, however, is somewhat lower than the corresponding world average, and therefore tends to increase the one-prong problem.

Highlights

  • Since the discovery of the x lepton [1] in e÷e - ~z+z, a large number of groups at various laboratories have investigated its properties [2]

  • In this paper we present the results of a high statistics analysis of the z decay modes x± ~h±n°v and z ± ~h±n°n°v, where h ± is a charged hadron

  • For no energies above 500 MeV, it becomes increasingly likely that the photon showers overlap, giving a single elongated energy deposition. Such "merged" n°'s are identified by method (2), which is an analysis of the shape of the energy deposition, yielding the invariant mass and the direction cosines of the parent n°

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Summary

18 April 1991

Measurement of the branching ratios for the decays x- hadron n°v and x--,hadron n°n°v. UniversiRit Wiirzburg 13, I4:-8700 Wiirzburg, FRG m California Institute o f Technology ~4 Pasadena, CA 91125, USA. The Crystal Ball detector at the DORIS II storage ring at DESY has been used to measure the branching ratios for the decay modes x±-~h±n°v and x+-~h±n°n°v, where h ± is any charged hadron. The results are B R ( x ± - , h ± n ° v ) = 8 -+ 1.9)%, BR (x ± ~ h ±n°n°v) = (5.7 _+0.5_+I~7)% The first result is in good agreement with the present world average. Its branching ratio is somewhat lower than the corresponding world average, and tends to increase the one-prong problem

Introduction
Present address
Detector
Monte Carlo simulation
Data sample
Analysis method
General cuts
Results
10. Conclusions
Full Text
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