STAR實驗是位於美國布魯克海文國家實驗室(Brookhaven National Laboratory)，相對論性重離子對撞機(Relativistic Heavy Ion Collider)中，最主要的實驗之一。最近，STAR實驗安裝了新的渺子探測器 -- Muon Telescope Detector (MTD)。在2013年時，完成了約63%的安裝，並於2014年全部安裝完成。這是我們第一次能夠在STAR使用雙渺子衰變去研究Quarkonia的物理。

我們使用了三種方法在2013年收集的質心能量為500 GeV的質子質子對撞數據中研究了渺子辨別的分析。結果表示，三種方法都能夠在p_T 〉 3 GeV/c的範圍裡有高於80%的辨別效率。

另外，我們也應用了渺子辨別分析的結果研究J/psi粒子在相同的實驗數據中的生成截面(production cross section)。我們的結果跟使用雙電子衰變的分析結果，在p_T重疊的區域是非常吻合的，並且也非常符合CGC+NRQCD理論的預測。

The Solenoid Tracker at RHIC (STAR) is one of the major experiments in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. In 2013, a new detector – Muon Telescope Detector (MTD) is installed about 63% of the full system and completely installed in 2014. It provides an excellent opportunity to study heavy quarkonia physics using dimuon channel in the experiments.

We studied the muon identification using three different methods with proton-proton collision at sqrt(s) = 500 GeV data collected in 2013. The result shows that the muon identification efficiencies reaches about 80% with p_T 〉 3 GeV/c.

The measurement of the J/psi invariant cross section is also studied using dimuon decay channel with Likelihood Ratio method for muon identification. The results in dimuon channel are consistent with the results in dielectron channel in the overlap p_T region and have good agreement with the CGC+NRQCD prediction.

Abstract in Chinese .................. ................. i
Abstract in English ................................... ii
Acknowledgements................................... iii
Contents......................................... v
List of Tables ...................................... viii
List of Figures...................................... x
1 Introduction..................................... 1
2 Theory Reviews................................... 3
2.1 The Standard Model of particle physics ................... 3
2.2 Charmonium states and the J/ψ productions................... 6
2.3 Quantum Chromodynamics (QCD) and Quark-gluon Plasma (QGP) ................... 8
3 Experimental Setup ................................. 12
3.1 Relativistic Heavy Ion Collider........................ 12
3.2 The STAR detector .............................. 12
3.3 Magnet System ................................ 14
3.4 Time Projection Chamber (TPC)....................... 14
3.5 Time-of-Flight (ToF) ............................. 15
3.6 Muon Telescope Detector (MTD) ...................... 17
4 Data Samples .................................... 19
4.1 Datasets and the basic selections....................... 19
4.2 Monte Carlo Samples............................. 21
5 Muon Identification................................. 24
5.1 Muon candidates selections.......................... 24
5.2 Straight cut method.............................. 24
5.3 N-1iteration method ............................. 26
5.4 Likelihood ratio method ........................... 28
5.5 The muon identification efficiencies ..................... 29
5.5.1 Tag-and-Probe method........................ 29
5.5.2 Statistical errors ........................... 32
5.6 Systematic uncertainties ........................... 33
5.6.1 Signal extraction ........................... 33
5.6.2 Building the PDF ratios ....................... 34
5.6.3 pT smearing of the MC muons.................... 35
5.7 Results..................................... 36
6 Measurement of J/ψ cross section ......................... 43
6.1 Event selections................................ 43
6.2 J/ψ signal extraction............................. 43
6.3 J/ψ efficiencies and acceptances....................... 44
6.3.1 Vertex finding efficiency....................... 45
6.3.2 TPC tracking efficiency and TPC acceptance ......................47
6.3.3 MTD matching, MTD response, MTD trigger efficiencies and MTD acceptance .............................. 49
6.3.4 Muon identification efficiency.................... 51
6.4 Systematic uncertainties ........................... 53
6.4.1 Signal extraction ........................... 53
6.4.2 TPC tracking efficiency ....................... 54
6.4.3 MTD response efficiency....................... 55
6.4.4 Muon identification.......................... 56
6.4.5 Total uncertainties .......................... 58
6.5 Results .................................. 60
6.6 Future work.................................. 61
7 Conclusions..................................... 64
References........................................ 65
Appendix A Fitting results............................... 69
A.1 Fit results for muon identification efficiency ............................ 70
A.1.1  Single Gaussian function + 3rd order polynomials ....................70
A.1.2  Single Gaussian function + 4th order polynomials .................... 71
A.1.3  CrystalBallfunction+3rd order polynomials .................... 73
A.1.4  CrystalBallfunction+4th order polynomials .................... 74
A.1.5 Fits for Likelihood Ratio method using the PDF ratios with different methods................................ 76
A.2 Signal extraction for the cross section using different fit models ............................... 78
Appendix B Non-prompt J/ψ Fraction........................ 80
B.1 Event selections................................ 80
B.2 J/ψ-hadron correlation............................ 80
B.3 Results..................................... 83
B.4 Futurework.................................. 84

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