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Annual Modulation Study of Dark Matter Using CsI(Tl) crystals in KIMS Experiment

DC Field Value Language
dc.contributor.advisor최선호-
dc.contributor.author최정훈-
dc.date.accessioned2017-07-14T00:55:35Z-
dc.date.available2017-07-14T00:55:35Z-
dc.date.issued2012-08-
dc.identifier.other000000003830-
dc.identifier.urihttps://hdl.handle.net/10371/121488-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2012. 8. 최선호.-
dc.description.abstractDark Matter contributes about 23% of the total energy and matter in the Universe and encloses galaxies by a halo of WIMPs in particular model. The Sun revolves around the center of the Milky Way and its dark matter halo and the earth also revolves around the Sun at the speed of 30 km/s with the inclined angle of 60 degree. Therefore, the earth can interact with the dark matter wind, which is expected to be stronger in the summer than in the winter. The DAMA group reported the annual modulation effect of 0.0183 ± 0.0022 cpd/kg/keV (2-4 keVee) with 8.3σ in 1 cpd/kg/keV background leve with their NaI(Tl) crystal detectors. The KIMS experiment with CsI(Tl) crystal detectors has been looking for dark matter signals and can be expected to see a similar annual modulation effect if the DAMA result is due to dark matter. The status of the KIMS annual modulation study with a 2.5 year exposure is reported.-
dc.description.tableofcontents1 Introduction 1
1.1 Concordance Model of Universe - CDM . . . . . . . . . . . . 1
1.2 Dark Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3 WIMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.1 Supersymmetry & WIMP . . . . . . . . . . . . . . . . 10
1.3.2 WIMP-nucleon Scattering . . . . . . . . . . . . . . . . 15
1.4 Annual Modulation . . . . . . . . . . . . . . . . . . . . . . . . 17
1.4.1 Dark Matter Halo of the Milky Way . . . . . . . . . . 18
1.4.2 Annual Modulation of Interaction Rate . . . . . . . . . 20
2 Experiment 24
2.1 Yangyang Underground Laboratory . . . . . . . . . . . . . . . 24
2.2 Detector Structure . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2.1 Shield Structure . . . . . . . . . . . . . . . . . . . . . . 27
2.2.2 4 × 3 Array of CsI(Tl) crystal Modules . . . . . . . . . 30
2.3 CsI(Tl) crystal . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.4 Data Acquisition System . . . . . . . . . . . . . . . . . . . . . 38
2.4.1 Electronics & DAQ . . . . . . . . . . . . . . . . . . . . 38
2.4.2 Trigger Efficiency . . . . . . . . . . . . . . . . . . . . . 43
2.5 Environment Monitoring . . . . . . . . . . . . . . . . . . . . . 45
2.5.1 Environment Stability . . . . . . . . . . . . . . . . . . 45
2.5.2 Network Status . . . . . . . . . . . . . . . . . . . . . . 46
2.5.3 UPS Monitoring . . . . . . . . . . . . . . . . . . . . . . 46
2.5.4 Temperature & Humidity . . . . . . . . . . . . . . . . 46
2.5.5 Surface Temperature of 12 CsI(Tl) crystals . . . . . . . 49
2.5.6 HV monitoring . . . . . . . . . . . . . . . . . . . . . . 52
2.5.7 KIMS DAQ Job Status . . . . . . . . . . . . . . . . . . 52
3 Analysis 57
3.1 Data Taking And Stability . . . . . . . . . . . . . . . . . . . . 57
3.2 Signal & Cluster . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.3 Energy Calibration . . . . . . . . . . . . . . . . . . . . . . . . 61
3.4 Event Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 65
3.4.1 Electronics Noise . . . . . . . . . . . . . . . . . . . . . 65
3.4.2 Partial Charge . . . . . . . . . . . . . . . . . . . . . . 67
3.4.3 Partial Charge . . . . . . . . . . . . . . . . . . . . . . 67
3.4.4 Charge Asymmetry . . . . . . . . . . . . . . . . . . . . 69
3.4.5 Start Time . . . . . . . . . . . . . . . . . . . . . . . . 71
3.4.6 Time asymmetry . . . . . . . . . . . . . . . . . . . . . 74
3.4.7 Fig Quality . . . . . . . . . . . . . . . . . . . . . . . . 77
3.4.8 Correlation of Selection Conditions . . . . . . . . . . . 77
3.5 Efficiency & Energy Spectrum . . . . . . . . . . . . . . . . . . 79
3.5.1 Effect of Event Selection . . . . . . . . . . . . . . . . . 79
3.5.2 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.6 Background Reduction . . . . . . . . . . . . . . . . . . . . . . 86
3.7 Fitting Function . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.7.1 Time Plot of Event Rate . . . . . . . . . . . . . . . . . 94
3.7.2 Fitting Function . . . . . . . . . . . . . . . . . . . . . 94
3.8 Annual Modulation Search . . . . . . . . . . . . . . . . . . . . 98
3.8.1 Search For Annual Modulation . . . . . . . . . . . . . 98
3.8.2 Variable of N0 . . . . . . . . . . . . . . . . . . . . . . . 98
3.8.3 Variable of b0 . . . . . . . . . . . . . . . . . . . . . . . 99
3.8.4 Variable of amplitude . . . . . . . . . . . . . . . . . . . 99
3.8.5 Goodness of Fit . . . . . . . . . . . . . . . . . . . . . . 108
3.9 Averaged Result . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.9.1 Single Hit Events . . . . . . . . . . . . . . . . . . . . . 117
3.9.2 Multiple Hit Events . . . . . . . . . . . . . . . . . . . . 120
3.9.3 Summary of Annual Modulation . . . . . . . . . . . . . 120
3.9.4 Direct Fitting For Energy Intervals . . . . . . . . . . . 125
3.9.5 Except DET10 . . . . . . . . . . . . . . . . . . . . . . 125
3.10 χ2 Fitting & Parameters . . . . . . . . . . . . . . . . . . . . . 132
3.10.1 Parameter Correlation . . . . . . . . . . . . . . . . . . 132
3.10.2 χ2 Fitting of Parameters . . . . . . . . . . . . . . . . . 137
4 System Stability 141
4.1 Time Dependent Systematics . . . . . . . . . . . . . . . . . . 141
4.2 Gain Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
4.3 Surface Temperature of CsI(Tl) cryatals . . . . . . . . . . . . 142
4.4 Temperature and Humidity of Halls . . . . . . . . . . . . . . . 146
5 Conclusion and Discussion 149		-
dc.formatapplication/pdf-
dc.format.extent7751941 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectdark matter-
dc.subjectWIMP-
dc.subjectKIMS-
dc.subjectannual modulation-
dc.subject.ddc523-
dc.titleAnnual Modulation Study of Dark Matter Using CsI(Tl) crystals in KIMS Experiment-
dc.typeThesis-
dc.contributor.AlternativeAuthorJungHoon Choi-
dc.description.degreeDoctor-
dc.citation.pagesxiii,154-
dc.contributor.affiliation자연과학대학 물리·천문학부(물리학전공)-
dc.date.awarded2012-08-
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