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ECAL Digitization

Rick Wilkinson May 25, 2006. ECAL Digitization. 1. CaloHitResponse. CaloSamples (analog signal). EcalElectronicsSim. EBDataFrame EEDataFrame. ECAL Digitization. SimHits. (EB ieta -17, iphi84 ; ism 23 , ic 324) 10 samples ADC=198, gainId=2 ADC=199, gainId=2

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ECAL Digitization

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  1. Rick Wilkinson May 25, 2006 ECAL Digitization 1

  2. CaloHitResponse CaloSamples (analog signal) EcalElectronicsSim EBDataFrame EEDataFrame ECAL Digitization SimHits (EB ieta -17, iphi84 ; ism 23 , ic 324) 10 samples ADC=198, gainId=2 ADC=199, gainId=2 ADC=195, gainId=2 ADC=358, gainId=2 ADC=409, gainId=2 ADC=376, gainId=2 ADC=317, gainId=2 ADC=260, gainId=2 ADC=220, gainId=2 ADC=198, gainId=2 2

  3. Photoelectrons per GeV: • Barrel: 2500 • Endcap: 1800 • Leads to a stochastic energy resolution of: Barrel:Endcap: Photostatistics 3

  4. Shaping • ECAL charge collection much slower than HCAL • ECAL: 47.6 ns peaking time • HCAL: 14 ns • HF: 2 ns • Requires more samples for reconstruction • ECAL: uses 5 samples • HCAL: 2 • HF: 1 • More sensitive to pileup • No jitter effect added 4

  5. Sources of Noise • PEDESTAL NOISE: • Barrel: 40 MeV • Endcap: 150 MeV • GAIN VARIATIONS: • Intrinsic (light collection uniformity) • 0.3% smearing in simulation • Calibration uncertainty • NOT simulated • To be included by other methods • Database? • External smearing tools? • Goal: 0.5% 5

  6. SimHits Made by GEANT4 Simulation step Contains: • Energy • Time-of-flight • SimTrack ID One SimHit is created for each: • Generator particle • Detector Unit • Nanosecond of shower development

  7. Encoding • Energy encoded into 12 bits by Multi-Gain Preamplifier (MGPA) • Gains of 1, 6, and 12 • Gain 12: 1 ADC = 35 MeV (barrel), 60 MeV (endcap) • Gain 6: 1 ADC = 70 MeV (barrel), 120 MeV (endcap) • Gain 1: 1 ADC = 420 MeV (barrel), 720 MeV (endcap) • Saturates at 1.7 TeV (barrel), 2.95 TeV (endcap) • Hysteresis effect: once a gain is switched up, it stays up for 5 samples. 8

  8. Calibration & Condition Databases • ECAL digitization doesn't use these interfaces yet • uses configurable parameters now • The interfaces exist. We could retrieve, channel-by-channel: • Pedestals & pedestal widths • Intercalibration constant, mean and sigma • Calibration: ADC to GeV • Gain ratios: 12/6 and 6/1 • Weights for reconstruction 9

  9. Trigger Towers • Barrel geometry is simple • One ECAL trigger tower equals: • 25 crystals • One HCAL tower • Endcap Geometry is not simple 10

  10. Selective Readout Being implemented now • High Interest EM Trigger Tower (> 5 GeV) • Take all crystals from: • This tower • Neighboring towers • Medium Interest EM trigger tower (> 2.5 GeV) Take all crystals in this tower • Low Interest • Barrel threshold: 90 MeV • Endcap threshold: 450 MeV • Remember, noises were 40 MeV and 150 MeV 11

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