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Study of tau lepton decays involving K0S at Belle
DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | 최선호 | - |
dc.contributor.author | 류수 | - |
dc.date.accessioned | 2017-07-14T00:55:14Z | - |
dc.date.available | 2017-07-14T00:55:14Z | - |
dc.date.issued | 2012-08 | - |
dc.identifier.other | 000000003330 | - |
dc.identifier.uri | https://hdl.handle.net/10371/121484 | - |
dc.description | 학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부(물리학전공), 2012. 8. 최선호. | - |
dc.description.abstract | The τ lepton is the only known lepton massive enough to decay into hadrons via a weak vector current, and this provides a sensitive probe of the standard model parameters, | - |
dc.description.abstract | Vus | - |
dc.description.abstract | , αs and ms. However, because of the limited numbers of τ+τ− events, the hadronic decays involving kaons in τ lepton which is directly related to | - |
dc.description.abstract | determination has not been well studied for the decades.
The Belle experiment provides the best environments for studying τ leptons because of the high luminosity of e+e− collisions result in the production of large numbers of τ+τ− events. We report measurements of branching fractions for inclusive/exclusive τ decays involving K0S → π−π+ with 669 fb−1 accumulated data at Belle detector at the asymmetric energy KEKB e+e− collider. The branching fraction measured for the inclusive decay is B(τ− → K0S X−ν ) = (0.910±0.001±0.046)%, where X− can be anything | - |
dc.description.abstract | for exclusive decays we report:
B(τ− → π−K0S ν ) =(4.10 ± 0.01 ± 0.21) × 10−3 B(τ− → K−K0S ν ) =(7.09 ± 0.06 ± 0.41) × 10−4 B(τ− → π−K0S π0ν ) =(1.95 ± 0.02 ± 0.11) × 10−3 B(τ− → K−K0S π0ν ) =(7.31 ± 0.12 ± 0.49) × 10−4 We also studied decays involving two K0S: B(τ− → π−K0SK0Sν ) =(2.41 ± 0.04 ± 0.26) × 10−4 B(τ− → π−K0SK0Sπ0ν ) =(2.06 ± 0.23 ± 0.24) × 10−5 where B(τ− → π−K0SK0Sπ0ν ) is the first measurement. We also report the first observation of the channel τ− → f1(1285)-ν in π−K0SK0Sπ0 decay with its total branching fraction of (1.07±0.23±0.16)×10−5. With these results, we expect the most precise value of | - |
dc.description.abstract | can be achieved. | - |
dc.description.tableofcontents | Contents
1 Introduction 1 1.1 The τ lepton . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1.1 τ pair production . . . . . . . . . . . . . . . . . . . . . 2 1.1.2 Branching fraction . . . . . . . . . . . . . . . . . . . . 3 1.2 Hadronic τ decay . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.2.1 Hadronic decays and their structures . . . . . . . . . . 14 1.2.2 Spectral function . . . . . . . . . . . . . . . . . . . . . 22 1.2.3 | - |
dc.description.tableofcontents | Vus | - |
dc.description.tableofcontents | and ms . . . . . . . . . . . . . . . . . . . . . . . . 25
1.3 | - |
dc.description.tableofcontents | and τ decays . . . . . . . . . . . . . . . . . . . . . . . . 27
1.3.1 Cabbibo Kobayashi Maskawa(CKM) matrix . . . . . . 27 1.3.2 Measurements of CKM matrix elements . . . . . . . . 28 1.3.3 | - |
dc.description.tableofcontents | determination in hadronic τ decays . . . . . . . . 31
1.4 Outline of thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2 B-factory 37 2.1 KEKB storage ring . . . . . . . . . . . . . . . . . . . . . . . . 40 2.1.1 Physical requirements . . . . . . . . . . . . . . . . . . 40 2.1.2 Accelerator Design . . . . . . . . . . . . . . . . . . . . 43 2.1.3 Performance . . . . . . . . . . . . . . . . . . . . . . . . 46 2.2 The Belle Detector . . . . . . . . . . . . . . . . . . . . . . . . 48 2.2.1 Extreme Forward Calorimeter(EFC) . . . . . . . . . . 48 2.2.2 Silicon Vertex Detector(SVD) . . . . . . . . . . . . . . 50 2.2.3 Central Drift Chamber(CDC) . . . . . . . . . . . . . . 54 2.2.4 Aerogel threshold Chrenkov Counters(ACC) . . . . . . 60 2.2.5 Time-of-flight Counters(TOF) . . . . . . . . . . . . . . 64 2.2.6 Electromagnetic Calorimeter(ECL) . . . . . . . . . . . 68 2.2.7 K0L and Muon Detection System(KLM) . . . . . . . . . 72 2.2.8 Trigger . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2.2.9 Data Acquisition System(DAQ) . . . . . . . . . . . . . 79 2.2.10 Computing Systems and Softwares . . . . . . . . . . . 82 2.2.11 Monte Carlo simulation in τ analysis . . . . . . . . . . 85 3 τ+τ− event selection 89 3.1 Pre-selection of τ events . . . . . . . . . . . . . . . . . . . . . 89 3.2 Selection of hadronic τ decays . . . . . . . . . . . . . . . . . . 95 3.2.1 K0S selection . . . . . . . . . . . . . . . . . . . . . . . 99 3.2.2 π0 selection . . . . . . . . . . . . . . . . . . . . . . . . 102 3.2.3 Particle Identification . . . . . . . . . . . . . . . . . . 102 3.2.4 τ− → K0S (particles)−ν events . . . . . . . . . . . . . 105 3.2.5 τ− → π−(K−)K0S ν . . . . . . . . . . . . . . . . . . . 105 3.2.6 τ− → π−(K−)K0Sπ0ν . . . . . . . . . . . . . . . . . . 105 3.2.7 τ− → π−K0SK0S(π0)ν . . . . . . . . . . . . . . . . . . . 107 3.3 Selection of e-μ events . . . . . . . . . . . . . . . . . . . . . . 110 4 Data analysis 115 4.1 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 4.1.1 The event selection efficiency . . . . . . . . . . . . . . 116 4.1.2 Corrections for the particle ID . . . . . . . . . . . . . . 118 4.1.3 Correction for K0S efficiency . . . . . . . . . . . . . . . 119 4.1.4 Correction to π0 efficiency . . . . . . . . . . . . . . . . 119 4.1.5 Efficiency dependence on hadronic current . . . . . . . 119 4.1.6 Efficiency of Sgg sideband subtraction . . . . . . . . . . 125 4.2 Background estimation . . . . . . . . . . . . . . . . . . . . . . 126 4.2.1 Non-π0 background . . . . . . . . . . . . . . . . . . . 128 4.2.2 Continuum background . . . . . . . . . . . . . . . . . 131 4.2.3 Background from τ− → π−K0SK0Lπ0ν decays . . . . . 132 4.2.4 Summary of the background . . . . . . . . . . . . . . . 133 5 Determination of the branching fractions 139 5.1 Method of branching fraction calculation . . . . . . . . . . . . 139 5.2 The branching fraction measurement . . . . . . . . . . . . . . 140 5.2.1 For inclusive decay . . . . . . . . . . . . . . . . . . . . 140 5.2.2 For the decays with one K0S . . . . . . . . . . . . . . . 141 5.2.3 For the decays with two K0S . . . . . . . . . . . . . . . 146 6 Systematic uncertainties 153 6.1 Uncertainty from the normalization . . . . . . . . . . . . . . 154 6.1.1 △Be and △Bμ . . . . . . . . . . . . . . . . . . . . . . . 154 6.1.2 △ǫe-μ contribution . . . . . . . . . . . . . . . . . . . . 155 6.1.3 △Ne-μ and △Be-μ . . . . . . . . . . . . . . . . . . . . 156 6.1.4 Luminosity . . . . . . . . . . . . . . . . . . . . . . . . 157 6.2 Uncertainty from background estimation . . . . . . . . . . . . 157 6.3 Uncertainty from efficiencies . . . . . . . . . . . . . . . . . . . 158 6.3.1 Tracking efficiency . . . . . . . . . . . . . . . . . . . . 159 6.3.2 Charged pion/Kaon ID efficiency . . . . . . . . . . . . 159 6.3.3 K0S efficiency . . . . . . . . . . . . . . . . . . . . . . . 159 6.3.4 π0 efficiency . . . . . . . . . . . . . . . . . . . . . . . . 160 6.3.5 Dependency on hadron model . . . . . . . . . . . . . . 160 6.3.6 Trigger efficiency . . . . . . . . . . . . . . . . . . . . . 161 6.3.7 Effect from γ veto . . . . . . . . . . . . . . . . . . . . . 161 6.4 Summary of systematic uncertainty . . . . . . . . . . . . . . . 162 7 Conclusions 165 A π0 efficiency study using τ− → π−π0ν 177 A.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 A.2 Event selection . . . . . . . . . . . . . . . . . . . . . . . . . . 180 A.2.1 Data sample . . . . . . . . . . . . . . . . . . . . . . . . 180 A.2.2 Selection Criteria . . . . . . . . . . . . . . . . . . . . . 180 A.2.3 The general features of τ− → ππ0ν candidates . . . . 182 A.3 Branching ratios and Efficiency corrections . . . . . . . . . . 186 A.3.1 For single ππ0 event . . . . . . . . . . . . . . . . . . . 186 A.3.2 For double ππ0 event . . . . . . . . . . . . . . . . . . . 187 A.4 Systematic Uncertainty . . . . . . . . . . . . . . . . . . . . . . 194 A.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 | - |
dc.format | application/pdf | - |
dc.format.extent | 16462105 bytes | - |
dc.format.medium | application/pdf | - |
dc.language.iso | en | - |
dc.publisher | 서울대학교 대학원 | - |
dc.subject | tau lepton | - |
dc.subject | hadronic decays | - |
dc.subject | Vus | - |
dc.subject | Belle | - |
dc.subject.ddc | 523 | - |
dc.title | Study of tau lepton decays involving K0S at Belle | - |
dc.type | Thesis | - |
dc.description.degree | Doctor | - |
dc.citation.pages | 227 | - |
dc.contributor.affiliation | 자연과학대학 물리·천문학부(물리학전공) | - |
dc.date.awarded | 2012-08 | - |
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