Universit`a degli studi Roma Tre Measurement of the KL meson ...

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48 CHAPTER 4. DATA SAMPLE AND KL TAG • BA: the barrel, RT < 200 cm and |z| < 150 cm; • EC: the endcaps, 25 cm < RT < 175 cm and |z| > 170 cm; • OV: the barrel-endcap overlap region, RT > 200 cm and |z| > 150 cm, or RT > 175 cm and |z| > 170 cm.
Chapter 5 Data analysis 5.1 Introduction The KL lifetime has been measured using the decay channel KL → π 0 π 0 π 0 . The choice of the fully neutral decay is intended to minimize the superposition with the KS → π + π − decay products. In fact, the tagging efficiency is almost independent of the KL decay length as shown in Fig. 4.3 thus minimizing the systematic error of the efficiency. This analysis makes use of ∼1.2 fb −1 data sample taken in 2005. The data set has been divided in periods having approximately the same value of √ s. The branching ratio of φ → KSKL is ∼34%. The signal of KL meson production is given by the observation of the KS → π + π − decay (see Sec. 4.2). As mentioned in the thesis introduction, this measurement has been already performed by KLOE in 2005 (Ref. [2]), but also if the technique of the measurement presented in this thesis is similar, there are many differences between the two: • the bunch crossing period has been lowered from 5.43 to 2.715 ns; this adjustment yielded an increase of machine background, and a finer analysis was needed to cope with the latter; • the tagging requests are slightly different: stronger cuts have been applied to preserve data quality, due to the short bunch crossing period; • the time calibration and the neutral vertex spatial resolution have been studied for each run period; • the single-photon neutral vertex reconstruction efficiencies as a function of the KL vertex position and the photon energy have been measured on data and applied on the Monte Carlo with a hit or miss method; • the machine background measured in data has been included run-by-run in the Monte Carlo program; • the background rejection selections are different; • the fit technique is much different: while in the previous measurement the data proper time distribution was efficiency corrected and background subtracted 49
Page 1: Università degli studi Roma Tre Di
Page 5 and 6: Contents 1 Neutral kaon physics wit
Page 7 and 8: Introduction The KLOE experiment ha
Page 9 and 10: Chapter 1 Neutral kaon physics with
Page 11 and 12: 1.2. MASS AND DECAY MATRICES 11 Γ
Page 13 and 14: 1.4. THE QUARK-MIXING MATRIX 13 rel
Page 15 and 16: 1.4. THE QUARK-MIXING MATRIX 15 s13
Page 17 and 18: 1.5. DETERMINATION OF THE |VUS| MAT
Page 19 and 20: Chapter 2 The DAΦNE collider DAΦN
Page 21 and 22: ËÁÇÆÃÇÆÆÀÊÇÆÈÀËÁË
Page 23 and 24: ØÖÒØ×Ô¬×ØÓÒ×ÓÖÒØ¬
Page 25 and 26: 3.1. THE DRIFT CHAMBER 25 Figure 3.
Page 27 and 28: ÇËËÁÄÍÁÂÄÊÆÁÆÁËÅÁ
Page 29 and 30: 3.2. THE CALORIMETER 29 Figure 3.6:
Page 31 and 32: 3.2. THE CALORIMETER 31 Figure 3.7:
Page 33 and 34: 3.3. THE TRIGGER 33 3.3 The trigger
Page 35 and 36: 3.5. FILFO FILTERING 35 are associa
Page 37 and 38: 3.6. EVENT RECONSTRUCTION 37 • ca
Page 39 and 40: 3.6. EVENT RECONSTRUCTION 39 Figure
Page 41 and 42: Chapter 4 Data Sample and K L tag M
Page 43 and 44: 4.2. THE KL TAG 43 to GEANFI using
Page 45 and 46: 4.2. THE KL TAG 45 As explained in
Page 47: 4.2. THE KL TAG 47 while the good a
Page 51 and 52: 5.1. INTRODUCTION 51 10 5 10 4 10 3
Page 53 and 54: 5.3. THE CONTROL SAMPLE KL → π +
Page 71 and 72: 5.4. KL → π 0 π 0 π 0 DECAY ID
Page 77 and 78: Chapter 6 Signal selection and back
Page 79 and 80: 6.1. BACKGROUND REJECTION 79 and N
Page 81 and 82: 6.2. NUCLEAR INTERACTIONS 81 Events
Page 83 and 84: 6.2. NUCLEAR INTERACTIONS 83 Figure
Page 85 and 86: 6.3. KL → KS REGENERATION 85 The
Page 87 and 88: Events / 1 MeV 6.4. NUCLEAR INTERAC
Page 89 and 90: Chapter 7 Fit results and errors 7.
Page 91 and 92: 7.1. FIT TO THE KL PROPER TIME DIST
Page 97 and 98: 7.2. CORRECTIONS AND SYSTEMATIC ERR
Page 99 and 100:
7.2. CORRECTIONS AND SYSTEMATIC ERR
Page 101 and 102:
7.2. CORRECTIONS AND SYSTEMATIC ERR
Page 103 and 104:
Chapter 8 Conclusions A measurement
Page 105 and 106:
By summarizing, the only correlated
Page 107 and 108:
Bibliography [1] K. G. Vosburgh et
Page 109:
BIBLIOGRAPHY 109 [31] M. Adinolfi e
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