Contents
1 Introduction
     1.1 Quark Gluon Plasma
     1.2 Collective Flow

2 The WA98 Experiment
     2.1 Calorimeter
     2.2 Charged Particle Tracking
         2.2.1 First Tracking Arm
         2.2.2 Second Tracking Arm
     2.3 Multiplicity Detectors
         2.3.1 Silicon Drift Detector
         2.3.2 Silicon Pad Multiplicity Detector
         2.3.3 Photon Multiplicity Detector
         2.3.4 Charged Particle Veto
     2.4 The Photon Spectrometer LEDA
         2.4.1 Mode of Operation
         2.4.2 Detector Design
     2.5 The Plastic Ball Spectrometer
     2.6 Trigger

3 Data Reduction
     3.1 Event Classification
     3.2 LEDA $\gamma$ and $\pi ^0$ Measurement
         3.2.1 Calibration and Corrections
         3.2.2 Photon Identification
         3.2.3 $\pi ^0$ Meson Reconstruction
     3.3 Plastic Ball
         3.3.1 Module Check
         3.3.2 Particle Identification
         3.3.3 Acceptance

4 Azimuthal Event Shape
     4.1 Reaction Plane Event by Event
         4.1.1 Sphericity Method
         4.1.2 Transverse Momentum Method
         4.1.3 Fourier Analysis Method
     4.2 Results
         4.2.1 $\Phi$ Distribution
         4.2.2 Subevent Analysis
         4.2.3 Dependence of $\chi$ on Centrality
         4.2.4 Reaction Plane Resolution
         4.2.5 Auto Correlation

5 Average Transverse Momentum
     5.1 Dependence of $\langle p_x \rangle$ on Rapidity
     5.2 Dependence of $\langle p_x \rangle$ on Centrality
     5.3 Dependence of $\langle p_x \rangle$ on Beam Energy

6 Azimuthal Correlation Analysis
     6.1 Dependence on Transverse Momentum
     6.2 Dependence on Rapidity
     6.3 Dependence on Centrality
     6.4 Comparison with $\langle p_x \rangle$ the Method

7 Summary and Conclusions

A Kinematical Variables
B Plastic Ball Mapping
C Event Selection
D Particle Identification
     D.1 The Applied Cuts
     D.2 Influence of cuts on $\langle p_x \rangle$
     D.3 Linearization Method
E Background Contamination
F Photon Flow Cross Checks

Bibliography
Acknowledgements