Abstract: The weak dipole moments of the tau lepton can be measured from the transverse components of the polarization. In this thesis the data collected in the L3 detector between 1991 and 1995, at a center of mass energy around the Z mass, are used to do the measurement. Besides, a test of Quantum Mechanics is done, using the sample selected for the weak dipole moments measurement.

Supervisor: Manuel Aguilar Benítez

Author: Eusebio Sánchez Alvaro (eusebio@ae.ciemat.es)

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Preface

1.- Introduction

1.1.- The Standard Model
1.1.1.- Interactions

1.1.2.- Matter

1.1.3.- Symmetry breaking sector

1.1.4.- Problems of the Standard Model

1.2 The tau lepton
1.2.1.- Neutral current couplings

1.2.2.- Charged current couplings

1.2.3.- QCD in tau decays

2.- The L3 experiment. Selection of the sample
2.1.- LEP

2.2.- The L3 experiment

2.2.1.- The magnet

2.2.2.- Central tracking system

2.2.3.- Electromagnetic calorimeter

2.2.4.- Luminosity monitor

2.2.5.- Scintillation counters

2.2.6.- Hadronic calorimeter

2.2.7.- Muon chambers

2.2.8.- Data adquisition system

2.3.- Selection of the sample
2.3.1.- Preselection

2.3.2.- Selection of tau hadronic decays

2.3.3.- Identification of neutral pions

3.- Weak dipole moments measurement
3.1.- Weak dipole moments and observables
3.1.1.- Weak dipole moments in the Standard Model

3.1.2.- Effective Lagrangian

3.1.3.- Weak dipole moments related observables

3.2.- Reconstruction of tau flight direction

3.3.- Analysis and results

3.3.1.- Analysis of selected sample

3.3.2.- CP symmetry of the detector

3.3.3.- Systematic errors

3.3.4.- Results

4.- An experiment about Quantum Mechanics at LEP
4.1.- Introduction

4.2.- Quantum Mechanics at LEP

4.2.1.- Proposed experiment

4.2.2.- The experiment does not exclude all the LHVT

4.3.- Analysis and experimental results
4.3.1.- Systematic errors

4.3.2.- Results

5.- Conclusions

Bibliography