声明
摘要
ABSTRACT
Contents
List of Tables
List of Figures
Chapter 1 Introduction
1.1 Standard model and Quantum Chromodynamics
1.1.1 Quantum Chromodynamics(QCD)
1.1.2 Running coupling
1.1.3 Chiral symmetry
1.1.4 Spontaneous breaking of chiral symmetry
1.1.5 Deconfinement and QGP
1.1.6 Restoration of the chiral symmetry
1.2 Dilepton production in high energy heavy ion collisions
1.3 Previous experiments and measurements
1.3.1 CERES/NA45
1.3.2 NA60
1.3.3 PHENIX
Chapter 2 Experiment set-up and detectors
2.1 The Relativistic Heavy Ion Collider
2.2 STAR experiment
2.2.1 STAR magnet system
2.2.2 Main tracker-Time Projection Chamber
2.2.3 Time Of Flight system
2.2.4 STAR trigger system
2.2.5 High Level Trigger/L4 system
2.3 Future upgrade
Chapter 3 Analysis
3.1 Data set and event selection
3.2 Centrality definition
3.3 Track selection and electron identification
3.3.1 Track selection
3.3.2 Electron identification
3.3.3 Hadron contamination and electron purity
3.4 Pair reconstruction and background
3.4.1 Like-sign method
3.4.2 Mixed event method
3.4.3 Photon conversion
3.4.4 Centrality and peeT dependence
3.4.5 Dielectron signal
3.5 Efficiency and acceptance correction
3.5.1 Single electron efficiency
3.5.2 Momentum resolution and energy loss
3.5.3 Pair efficiency and acceptance
3.5.4 Trigger efficiency,trigger bias and vertexing bias
3.5.5 The total correction factors for dielectron spectra
3.6 Hadronic cocktails
3.7 Systematic uncertainty
3.8 Combine the Au+Au results from year 2010 and year 2011
3.8.1 Comparison
3.8.2 Combination
Chapter 4 Result and discussion
4.1 Dielectron production in 200 GeV p+p collisions at STAR
4.2 Dielectron production in 200 GeV Au+Au collisions at STAR
4.2.1 Dielectron invariant mass spectra
4.2.2 Comparison to models
4.2.3 pT and centrality dependence
4.2.4 Correlated charm contributions
4.2.5 Low mass vector meson yields
4.2.6 mT slope parameters
4.3 Summary and outlook
Bibliography
Appendix
ACKNOWLEDGMENTS
Presentations and publication List