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

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36 CHAPTER 3. THE KLOE DETECTOR DAΦNE control Slow control Data Flow Controller (VME) SMP Run Control SMP Database server Calorimeters D E T E C T O R Tracking Chamber Trigger Digital Conversion and First Level Data Concentrator (10 VME chains) Calibration Data Packet Destination Assignment Events for online calibrations and data quality control VICbus Queue status message SMP server ROCK’s VIC FEE CPU FDDI Switch SMP server SMP tape server Tape library Cbus ROCKM one subevent per trigger 100 subevents per network packet VME-Second Level Data Concentrator and Sub-event builders 50 MBytes/s agregated throughput SMP server SMP tape server Figure 3.11: DAQ architecture. Trigger Supervisor (VME) Online Farm: Event builder, event filter, event recorder and monitor Events for offline reconstruction
3.6. EVENT RECONSTRUCTION 37 • calorimeter cluster reconstruction from single cells and evaluation of deposited energy and time of flight (as described in Sec. 3.2.1); • determination of the correct bunch crossing (see next Sec. 3.6.1); • rejection of machine-background and cosmic-ray events; • pattern recognition and track fitting for charged particles in the DC (see Sec. 3.1.1); • vertex reconstruction for charged particles (see Sec. 3.1.1); • association of DC tracks with calorimeter clusters (this algorithm will be explained in Sec. 3.6.2); • event classification (see next Sec. 3.6.3). 3.6.1 Bunch-crossing identification DAΦNE operates with 120 bunches per ring, that correspond to a bunch-crossing period TRF = 2.715 ns. Due to the short bunch-crossing period and the large spread of the particle arrival times, the trigger is not able to identify the bunch crossing related to each event, which has to be determined offline. The start signal for the electronics devoted to time measurement (TDC) is obtained by phase-locking the trigger level-1 signal (Sec. 3.3) to a replica of the RF frequency. The clock period is 4 ×TRF = 10.86 ns. The time measured by the TDC is then related to the time of flight of the particle from the event origin to the calorimeter, TTOF, by the formula: TTDC = TTOF + δC − NBCTRF (3.11) where δC is a single number accounting for the overall electronic offset and cable delay, and NBC is the number of bunch-crossings needed to generate the start to the TDC (see Fig. 3.12). The values of δC and TRF are determined for each data taking run with e + e − → γγ events. For such events, we look at the distribution of ∆TOF = Tclu − Rclu/c, where Rclu is the γ cluster position and Tclu is the γ cluster time reconstructed by the cluster algorithm applied to the TTDC (see Sec. 3.2.1): well separated peaks correspond to different values of NBC for events in the sample (see Fig. 3.13). δC is arbitrarily defined as the position of the peak with the largest statistics, and TRF is determined from the peaks time separation. Both quantities are evaluated with a precision of ∼4 ps in a run of 200 nb −1 of integrated luminosity. During offline processing, to allow the cluster times Tclu to correspond to particle times of flight TTOF, a time offset t0, evt ≡ δC − NBCTRF has to be subtracted from all cluster times (see Eq. 3.11). The time needed for the first level trigger formation,
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
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Page 25 and 26: 3.1. THE DRIFT CHAMBER 25 Figure 3.
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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: 3.5. FILFO FILTERING 35 are associa
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 and 48: 4.2. THE KL TAG 47 while the good a
Page 49 and 50: Chapter 5 Data analysis 5.1 Introdu
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
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Events / 1 MeV 6.4. NUCLEAR INTERAC
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Chapter 7 Fit results and errors 7.
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7.1. FIT TO THE KL PROPER TIME DIST
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7.2. CORRECTIONS AND SYSTEMATIC ERR
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Chapter 8 Conclusions A measurement
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By summarizing, the only correlated
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Bibliography [1] K. G. Vosburgh et
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BIBLIOGRAPHY 109 [31] M. Adinolfi e
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