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Much Noise About Nothing?

Much Noise About Nothing?. Robert Zitoun Stony Brook and LAPP CTF Meeting February 10, 2003. Channel noise. ADC noise depends on the cell size and/or the preamp: Larger cells -> larger noise Coarse hadronic

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Much Noise About Nothing?

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  1. Much Noise About Nothing? Robert Zitoun Stony Brook and LAPP CTF Meeting February 10, 2003 R. Zitoun, Stony Brook and LAPP CTF Meeting

  2. Channel noise • ADC noise depends on the cell size and/or the preamp:Larger cells -> larger noiseCoarse hadronic • Amplified by cal_weights(total to visible energy ratio)EM/HAD ~10 MeV/ADCCH ~ 30 MeV/ADC • ×1.6 for non linearity Noise/ADC Noise/GeV R. Zitoun, Stony Brook and LAPP CTF Meeting

  3. Channel noise 31 9 26 28 25 23 28 32 17 33 40 27 26 26 28 30 24 25 29 very high noise 96 91 89 107 104 117 ~40 70 ~90 • 1st line = raw noise/ADC 2nd = cal weights 3rd = noise/GeV >100 MeV R. Zitoun, Stony Brook and LAPP CTF Meeting

  4. Occupancy <Zero bias occ> for 450 runs 1%  ←100% ←15% • Zero suppression @ 2.5 s gaussian noise occupancy @ 1% a lot of good channels • BUT bad channels ugly channels • Remaining noise above 2.5 s is now at least EM/HAD ~ 300 MeV CH ~ 750 MeV R. Zitoun, Stony Brook and LAPP CTF Meeting

  5. Bad Channels 30 <ADC> 10- s rms 100% occupancy 40 ADC online pedestal 2.7— online s • Should be caught as early as possibleShifters should kill high occupancy channels and they should be replaced quickly R. Zitoun, Stony Brook and LAPP CTF Meeting

  6. Bad Channels – Effect on MET METx METy • Killing bad channels does good for MET<METx or y> before (•) and after (•) removals(METx or y) before (•) and after (•) removal R. Zitoun, Stony Brook and LAPP CTF Meeting

  7. Ugly channels • High occupancy ~10-15% • Several hypotheses studied • Pedestal shift • Non gaussian noise • L1 SCA dispersion + updown difference • Special calibration run R. Zitoun, Stony Brook and LAPP CTF Meeting

  8. Pedestal Shift (1) <ADC> online pedestal lower rounding upper rounding < > = 3.1 < > = –2.1 6ADC 1ADC R. Zitoun, Stony Brook and LAPP CTF Meeting

  9. Pedestal Shift - Macroscopic Effect –sum of rounded pedestals in a card  measured SET in card R. Zitoun, Stony Brook and LAPP CTF Meeting

  10. Pedestal shift (flop!) 10 <ADC> 10- s rms occupancy 10% 2 ADC online pedestal 4— online s • Pedestal shift does not explain ugly channels with high occupancy R. Zitoun, Stony Brook and LAPP CTF Meeting

  11. Gaussian Noise channel 52 (-15, 33, 3) rms = 2.17 s = 2.14 ↑rms ?? binning effect? s-rms • Non gaussian noise ? • Compare histo rms to gaussian fit s R. Zitoun, Stony Brook and LAPP CTF Meeting

  12. Non gaussian noise • Fix these channels, but what’s the problem? R. Zitoun, Stony Brook and LAPP CTF Meeting

  13. L1 SCA dispersion ADC counts cell # in L1 SCA • Noise comes mainly from calorimeter/preamp • Also from cell to cell dispersion in L1 SCA (much less in L2 SCA) R. Zitoun, Stony Brook and LAPP CTF Meeting

  14. L1 SCA up-down difference up down • More hardware to fix!!! R. Zitoun, Stony Brook and LAPP CTF Meeting

  15. Offline Zero Suppression • Data taken with 1.5s zero suppression • s from individual calibration runs • Reco suppresses at 2.5s • s from a special run taken on ~September 20 ~ 50 k events to average out any L1 SCA problems • Reco suppression with histo rmsMC generation with gaussian fit s → MC hot cells R. Zitoun, Stony Brook and LAPP CTF Meeting

  16. Offline Zero Suppression is sometimes wrong! pedestal normal noise level→ (symmetrized noise) ↑special run noise • offline suppression 2.5 × 2 = 5 ADC < online 1.5 × 4 ADC = 6 ADC • Same effect seen in most channels with high (~10%) occupancy good channel bad channel R. Zitoun, Stony Brook and LAPP CTF Meeting

  17. Suppression with 2.5 × online s before after • Implement 2.5 s cut on thumbnails and look at MET (bad cells not removed) • Certainly smoother distributions with lower rms R. Zitoun, Stony Brook and LAPP CTF Meeting

  18. Last Transparency, Mr Chairperson • Present calorimeter OK for x-section measurements • But lot of effort still needed to • fix the calorimeter (change boards and/or daughter cards) • understand its data (calibration strategy) • improve its resolution (not addressed here!) • Prepare a tool to clean the data (2.5 s cut, kill bad cells, ped shifts, ...) • Would be worth trying it on “noise” jets • Please do not drop CAL block from thumbnails before cal is OK • Let’s try a 2.5 s online cut R. Zitoun, Stony Brook and LAPP CTF Meeting

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