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Algorithm T42: Noise Suppression and Cell Selection in Calorimeter Data Reconstruction

This document outlines the T42 algorithm applied in calorimeter data processing, detailing its principles and implementation. The algorithm focuses on rejecting isolated medium cells, eliminating negative energy cells, and enhancing the selection of high-signal cells while preserving their significant neighbors. The T42 package includes various classes for managing cell lists and neighborhood information. Results from data sets indicate varying impacts on energy levels and cell rejection rates, prompting analysis of noise behavior and potential adjustments for specific regions, particularly those close to the beam.

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Algorithm T42: Noise Suppression and Cell Selection in Calorimeter Data Reconstruction

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  1. CAT plenary meeting T42 algorithm dedicated webpage :http://www-d0.fnal.gov/~vlimant/noise-suppdescr/Description.html • T42 + Top_analyze +d0root_analysis • Principle & Implementation • Effect on cells • Effect on EM objects VLIMANT Jean-Roch LPNHE 13 may 2003

  2. T42Principle : reject isolated medium cellsNamed after an algorithm used in H1 • Reject negative energy cells • Select high signal cells (4 sigma) • Keep their significant neighbours (2 sigma) Thresholds 2 is 2.5 at the moment

  3. cal_t42 Packagecreated after cal_nada classes Classes : • Calt42Struct : neighbourhood object • Calt42 : container for cell lists • Calt42Chunk : container for Calt42 object • Calt42Reco : • Does the cleaning and creates a Calt42Chunk with rejected cells and modify/or not the CalDataChunk (killing/shadow mode). • Get the neighbourhood info from a Calt42Struct object which allows a linear algorithm complexity. • Calt42Combine : • When shadow mode in d0reco : produces a clean CalDataChunk • When killing mode in d0reco : produces a un-clean CalDataChunk • And registerers RegCalt42Reco RegCalt42Combine

  4. Calt42Reco 1/2

  5. Calt42Reco 2/2

  6. Calt42Structclasscontent • Objects • spine : array[81600] of structured object • Mapped to ieta, iphi, layer by :INDEX = iphi + 64( layer - 1 ) + 1088( ieta + 37 ) - 1 • Structured object fields • sigma : tells the noise rms of the cell • pointers to all possible neighbors within the array • single pointer to be assigned to a CalCell available in CalDataChunk • Methods • Access • Fields initialiaser The Neighbourhood information is read from the file STRUCTURE.dat

  7. Calt42Structuse in Calt42Reco

  8. Calt42StructNeighbourhood informationhttp://www-d0.fnal.gov/~vlimant/noise-suppdescr/Description.html • How to check ? • Trust me • WebPage : check rules and pictures • Calt42Struct::PrintNeighbours(ieta,iphi,layer) • Calorimeter display : to be written

  9. Calt42CombineOnly for DST files Only one parameter • Do you want the t42 cleaned CalDataChunk ? Automatic detection of the d0reco mode by cell matching. Modification of the CalDataChunk

  10. In the frameworkneed for post-reconstruction when shadow mode For DST /TMB In the main rcp String packagename = “…unpack T42 rebuild …” T42 = < cal_t42 Calt42> // process the t42 algo or T42 = < cal_t42 Calt42Combine> // only combine chunks “rebuild” must reconstruct the object chunks you want to see the effect on

  11. Study effects on data Data sets • EM stream data 10000 evts of WZskim-emStream-*-*.raw_p13.06.01 under the project name WZstreamTMBp13.06 • Unstreamed data 10000 evts in files recoT_all_0000174234_mrg_*-*.raw_p14.01.00 Global_CMT run • Min/Zero bias Wzskim 10000 evts of Wzskim-mzbiasStream-*-*.raw_p13.06.01 Under the project name mzbias_mvh.all1

  12. Population reportunstreamed data

  13. Cells effectclose to beamEC regions • More rejection than expected noise ! • Too many cells with negative energy arbitrarily increases the rejection; They are not from gaussian noise only, probably due to pile-up • This is due to cell close to the beam 33-37 • Negative energy rejection is unsuited to this region • Should be treated separately • Keep untouched above |ieta|=33(CH) and 32 (EM, FH) • Even lower for FH ?

  14. Region Labels

  15. Region reportemstream data

  16. Region reportWZstream data with problems

  17. Region reportunstreamed data

  18. Region reportunstreamed data with problems

  19. Region reportminimum/zero bias data

  20. Region reportminimum/zero bias data with problems

  21. Cells effectaway from beamCC regions Statistically noise like rejection Always about the same number of negative cells in the event : probably noise and it is always rejected Coherent number of rejected cells Region occupancies show signal presence ~40% on unstreamed data Cells clustering decreases with the distance to interaction point -/+ rejected ratio for region threshold tuning ? Although skim dependent (topology dependence)

  22. Cells effectclose to the beam • Still too much rejection in FH part need to be investigate • Peaks are due to • Overpopulated cells • Cell with noise problem • strange regions ?

  23. Effect on EM clustersdata/MC sets • Zee picked sample p13.05 2418 evts (not used) • Filename : /rooms/living/varnes/scratch/cab/zee-p13/*/tmbfile • Zee Monte Carlo p13.08 6000 evts • Project name ctf_p13.08_zee_sig2.5_tmb • Filename : tmb-x13.08.00_CTF13.08.00-02-z-ee_np_mcp13_hepfm007.uta.edu_null_* • Estimators study • At high/low energy : emstream • At low energy : J/ skim from Jan Stark (not used yet)

  24. Effect on EM clustersNumber of cells

  25. Effect on EM clustersNumber of cells

  26. Effect on EM clustersestimators pT<13 GeV

  27. Effect on EMidestimators pT<13 GeV

  28. Effect on electronsestimators pT<13 GeV

  29. Effect on EM clustersestimators pT>13 GeV

  30. Effect on EMidestimators pT>13 GeV

  31. Effect on electronsestimators pT>13 GeV

  32. T42 effects • 10% more EM cluster (10,11 ) • 20% less above 13 GeV • 15% more Emid clusters • 80% more below 13GeV • 11% more electrons • 34% more below 13GeV

  33. EM Efficiency &fake ratesdata set • DIEM15 stream of WZ skim 1.5Mevt DIEM15-WZskim-emStream-*-*.raw_p13.06.01 (05) under the project name Wzskim_diem NEXT TIME

  34. Conclusion • Code run into p14 code • T42 chunk at DST level (checked) • D0note 4146 update soon • Noise cleaning • Electronic noise seems to be deleted • Pile-up problem near beam pipe remains • Get more electrons and photons • NEXT : • Fake and efficiency • More at low energy with J/ skim

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