Search for exotic tau decays

S Keh,K Wacker,U Strohbusch,K Königsmann,J Gaiser,R Cowan,M Reidenbach,J Irion,W Walk,G Conforto,S Leffler,R Lekebusch,T Kloiber,G Landi,K Fairfield,B Renger,J Schotanus,D Sievers,R Cabenda,M Scheer,I Kirkbride,F Messing,H Marsiske,B Muryn,K Strauch,B Lurz,G Folger,U Volland,K Brockmüller,T Kiel,K Wachs,D Gelphman,Z Jakubowski,P Schmitt,K Karch,C Rippich,D Antreasyan,W Maschmann,A Fridman,A Engler,B Van Uitert,D Besset,P Zschorsch,R Hofstadter,H Wegener,B Monteleoni,W Koch,V Stock,R Nernst,A Compagnucci,G Godfrey,J K Bienlein ,A M Cartacci ,D Williams,S Lowe,P N Ratoff ,F C Porter ,H W Bartels ,S Cooper,R.W Kraemer,S Krüger,P G Pelfer ,D Prindle,A S Schwarz ,K.j De Graaf ,W S Lockman ,M Kobel,H Vogel,F H Heinsius ,R Lee,G Nowak,E D Bloom ,A C König ,B Pollock,G Glaser,D G Coyne ,A.f Voigt ,H Janßen ,C Bieler ,R Clare,H Meyer,D Marlow,A Bizzeti,J Tompkins,B Niczyporuk,M Cavalli‐Sforza ,C Peck,I Brock,A M Litke ,F H Heimlich ,H J Trost ,H G Kilian ,T Skwarnicki,P Mcbride,J Schütte,W J Metzger ,R T Van De Walle

doi:10.1016/0370-2693(88)91248-8

Abstract

The Crystal Ball detector at the Doris II storage ring at DESY was used to search for the exotic decay processes τ→e γ, τ→e π 0, and τ→e η. No signal was observed. We obtained the following 90% CL upper limits on the branching fractions: B( τ→e γ)<2.0×10 −4, B( τ→e π 0)<1.4×10 −4, B( τ→e η)<2.4×10 −4.

Highlights

The standard model of electroweak and strong interactions has been very succesful phenomenologically
One of the most unsatisfactory features is the large number of arbitrary parameters: quark and lepton masses, mixing angles, W mass, Weinberg angle, etc., none of which is predicted within the standard model
It is possible that upper limits on a branching ratio can yield information on the scale at which the new physics begins to play a significant role

Summary

15 September 1988

BESSET d, Ch. BIELERe, J.K. BIENLEINc, A. CAVALLI - SFORZAd,[2], R. Universitgit Wiirzburg ~4,D-8700 Wiirzburg, Germany b Harvard University 9, Cambridge, MA 02138, USA. Deutsches Elektronen Synchrotron DESY, D-2000 Hamburg, Fed. Rep. Germany d Princeton University ~, Princeton, NJ 08544, USA. L InstitutJ~r Experimentalphysik 8, Universitiit Hamburg, D-2000 Hamburg, Fed. Rep. Germany r INFNand University of Florence, 1-50100Florence, Italy. Universitiit Erlangen-Niirnberg 7, D-8520 Erlangen, Germany J University of Nijmegen and NIKHEF ~o,NL-6525 ED Nijmegen, The Netherlands k Cracow Institute of Nuclear Physics, PL-30055 Cracow, Poland. The Crystal Ball detector at the Doris II storage ring at DESY was used to search for the exotic decay processes x ~ , x-~en°, and x--,er[1].

Introduction

Data sample and detector

Analysis

Event selection

Results

Discussion