LHC에서 ALICE를 이용한 f0(980)이 특징의 이해 = Understanding the nature of f0(980) with ALICE at the LHC

다국어 초록 (Multilingual Abstract)

The f0(980) resonance had been observed years ago in ππ scattering experiments and is expected to be one of the scalar mesons. Since its first observation in the 1970s, the nature of light scalar mesons is far from the understanding, and no consensus on its internal structure has been reached, raising different suggestions regarding the structure of the f0(980), such as tetraquark, mesonic molecule, and conventional diquark structure.
The extreme environment, such as high temperature and density, deconfines quarks and gluons, freeing them and forming the Quark-Gluon Plasma (QGP), which is expected to be created immediately after the Big Bang. Such an early stage of our universe can be reproduced in relativistic heavy ion collisions, providing chances to study the properties of QGP. Extensive studies have been conducted on the geometry, evolution, and particle production of QGP, and its modification, with many scientific acceptances for the existence of QGP. Surprisingly, phenomena exhibiting the existence of QGP are also observed in high-multiplicity proton–proton and proton–ion collisions, leading to further questioning QGP formation.
In this respect, the f0(980) resonance is measured with the ALICE detector via the f0(980) → π+π− decay channel in relativistic nucleus–nucleus collisions. The present thesis describes the entire methodology to measure the invariant yield in different multiplicity classes at midrapidity. The particle yield ratios of the f0(980) resonance are measured to discuss the properties of the late hadronic phase throughout different collision systems and to explore the internal structure of the f0(980). Furthermore, the measurement of the nuclear modification factor and the elliptic flow and model predictions with different assumptions for the f0(980) strengthen the physics messages in the present thesis.

목차 (Table of Contents)

• 1. Quark-Gluon Plasma and heavy ion collisions 6
• 1.1 Quantum Chromodynamics 7
• 1.2 Relativistic heavy ion collisions 9
• 1.2.1 Initial stage of collisions 10
• 1.2.2 Evolution of QGP 12
• 1.2.3 Freeze-out 12
• 1.3 Chemical freeze-out 13
• 1.4 Kinetic freeze-out 15
• 1.5 Collectivity 22
• 1.6 Partonic energy loss 25
• 1.7 Suppression of heavy quarkonium 28
• 2 QGP droplets in small systems 31
• 2.1 Anisotropic flow 31
• 2.2 Strangeness enhancement 38
• 2.3 Inconclusive measurements 39
• 2.3.1 Nuclear modification factor 40
• 2.3.2 Jet quenching 41
• 3 f0(980) resonances 43
• 3.1 Internal structure of f0(980) 44
• 3.2 f0(980) production at LHC energy 45
• 4 Experimental setup 47
• 4.1 Detection of charged-particles 47
• 4.1.1 Transverse momentum 47
• 4.1.2 Ionization energy loss 48
• 4.1.3 Time-of-Flight 50
• 4.1.4 Machine learning 50
• 4.2 Large Hadron Collider in CERN 51
• 4.3 ALICE detector 54
• 4.3.1 The V0 Detector 55
• 4.3.2 The ZDC Detector 58
• 4.3.3 The ITS Detector 61
• 4.3.4 The TPC Detector 62
• 4.3.5 The TOF Detector 63
• 4.3.6 Track reconstruction 64
• 5 Analysis method 66
• 5.1 Event Selection 66
• 5.1.1 Multiplicity estimator 67
• 5.2 Track Selection 69
• 5.3 Signal Extraction 70
• 5.4 Fit procedure 77
• 5.5 Correction 86
• 5.5.1 Normalization to NSD 86
• 5.5.2 Signal-Loss Correction 86
• 5.5.3 Acceptance X efficiency 89
• 5.5.4 Re-weighting procedure 89
• 6 Systematic uncertainties 91
• 7 Results 97
• 7.1 f0(980) in p-Pb collisions at sNN = 5.02 TeV 97
• 7.2 Extension to different collision systems 106
• 7.3 Event plane dependent production 111
• 8 Conclusions 114
• A Ridge and flow coefficients in small collision systems 117
• B Machine learning for the angular reconstruction of r 128
• C SHINCHON project 133
• C.1 Framework 133
• C.2 Results 137
• D Length-scale calibration in luminosity measurement 141
• D.1 Converted Run 2 data 141
• D.2 Usage of lumi.cxx 142
• D.2.1 Inputs 143
• D.2.2 Outputs 143
• D.3 Length-Scale calibration 143
• D.3.1 pp 143
• D.3.2 Pb-Pb 146
• D.4 Non-factorization analysis 147