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PHOS offline status report

PHOS offline status report. Yuri Kharlov ALICE offline week 6 July 2010. PHOS hardware status in P2. 3 modules (out of 5) are installed in positions 1, 2, 3: 260 <<320, |y|<0.13. 11/12 of FEE are alive and take data (960 channels out of 10752 are dead).

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PHOS offline status report

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  1. PHOS offline status report Yuri Kharlov ALICE offline week 6 July 2010

  2. PHOS hardware status in P2 • 3 modules (out of 5) are installed in positions 1, 2, 3: 260<<320, |y|<0.13. • 11/12 of FEE are alive and take data (960 channels out of 10752 are dead). • Noise conditions are satisfactory: 410 channels are noisy • Energy scale is 2 MeV/ADC instead of 5 designed MeV/ADC. The maximum measurable energy is 30 GeV instead of 100 GeV. • PHOS took part in all pp runs (LHC10b,c,d) triggered by ALICE minimum bias trigger. • Initial relative calibration of PHOS seemed to be at the level 20% in modules 2 and 3, 50% in module 4. PHOS offline status

  3. Fixed bugs in reconstruction • AliPHOSRawFitterv0: wrong treatment of low-gain amplitudes. https://savannah.cern.ch/bugs/?68008 • AliPHOSClustertizerv1: wrong application of calibration parameters to clusters. All cells in a cluster were calibrated with one and the same calibration parameter of the cluster seed. https://savannah.cern.ch/bugs/?68375 • Starting from v4-18-Rev-20, PHOS bugs were fixed. Used in pass2 reco. PHOS offline status

  4. PHOS DAs • PHOS had deployed 2 DAs and considered implementing one more: • PHOSGAINda.cxx – equalization of mean amplitude in all channels for relative calibration in physics runs • PHOSLEDda.cxx – calculation of high-gain/low-gain ratio in LED and physics runs • Apparently, bad channel map calculation is a rather complicated task. BCM was calculated from 4 sources: • Pedestal run: channels with R.M.S. of pedestals above a threshold are noisy • LED run with moderate amplitude: channels with deformed signal shape are noisy • LED runs with zero amplitude: channels with frequent false signals are noisy • Channels with energy deposited considerably larger than surrounding are noisy • Offline reconstruction with different bad channel maps allowed to choose the best BCM PHOS offline status

  5. Usage of online DA’s in PHOS • Change in preprocessor procedure: PHOSGAINda and PHOSLEDda are still running. Preprocessor puts the calibration objects to the reference CDB. Preprocessor also does: • calculates gains in PHYSICS runs from accumulated statistics and puts them to the production OCDB if Nentrues>1000 and if a channel is not bad. Validity range – 1 run. • calculates HG/LG ratio in LED runs is Nentries>2000. Validity range – (run-to-infinity). • Although 2 DA’s are running, their affect to the PHOS conditions is very limited: • Mapping the bad channels cannot be an automatic procedure, requires a human intervention and decision. • Noise appears and disappears. It can suddenly destroy firm calibration • Preprocessors simply copies gains and HG/LG ratios from the previous run, unless a very large statistics per run is accumulated. • We rely on conditions calculated offline only. PHOS offline status

  6. Offline calibration • Offline calibration is implemented as an analysis task and works with ESD or AOD. Requires the full available statistics. • Calibration algorithms: • Accumulating the cell energy histograms (10752 TH1F histograms): to search bad channels and to calculate mean deposited energy • Equalization of the mean deposited energy • Equalization of the number of hits per channel • Equalization of photostatistics from LED runs • pi0 peak width minimization. Implemented as an analysis task. • Calibration with pi0 requires a very large statistics (1 year of data taking). Hence, other calibration methods are looked for: less statistics, worse accuracy. • Any offline calibration procedure is a subject to validate by the pi0 peak width PHOS offline status

  7. Equalization of the mean cell energies:Data and software PHOS has requested 4 custom reconstructions of LHC10b,c (10-90 Mio events) to calculate the calibration parameters • Reco of LHC10c production ID PHOS_calib (http://alimonitor.cern.ch?75, AliRoot v4-18-Rev-20, 73 Mevents) was used to run offline calibration • Reco of LHC10c production ID PHOS_calib3 (http://alimonitor.cern.ch?84, AliRoot v4-18-Rev-20, 89 Mevents) was used to verify the new calibration PHOS offline status

  8. Recalibration performance Module 1 Module 3 Module 2 Several iterations (from 2 to 6) were enough to improve the pi0 peak width from 15 MeV to 9 MeV. PHOS offline status

  9. Recalibration of the worst module 4:before... PHOS offline status

  10. Recalibration of the worst module 4:after... PHOS offline status

  11. May 2010: inv.mass from reconstruction Module 1 • Module 1 was quite bad compared to module 2 and 3. • m (1) = 122 MeV/c2,  (1) = 30 MeV/c2 • m (2-3) = 134 MeV/c2, (2-3) = 17 MeV/c2 • Until improved calibration of module 1, need to discard it from the analysis Module 2 Module 3 PHOS offline status

  12. July 2010: Invariant mass from reconstruction Now all 3 modules are equally well calibrated. PHOS offline status

  13. Latest reconstruction: LHC10c pass2 All 3 PHOS modules PHOS offline status

  14. Inv.massvs pt in LHC10c pass2 reco PHOS offline status

  15. May 2010: 0 peak mass and width vs pt 0 peak width varied from 17 to 13 MeV/c2 PHOS offline status

  16. July 2010: 0 peak mass and width vs pt 0 peak width varied from 11 to 9 MeV/c2 PHOS offline status

  17. Correlation between iterations PHOS offline status

  18. How decalibration affects 0 peak width Simulated invariant mass spectra with different decalibration level 1: ideal calibration 2: 10% decalibration 3: 20% decalibration 4: 30% decalibration 5: 40% decalibration 6: 50% decalibration PHOS offline status

  19. PHOS alignment • Status has been surveyed in August 2009 just after the installation • Survey has provided the following data: • coordinates of the PHOS modules in the physicist reference system: displacement up to 1 cm (5 volumes) • coordinates of the PHOS strip units in the module local reference system: average displacement is 0.6 mm (1120 volumes) • Only PHOS modules misalignment affects physics and willbe provided to the official OCDB • Misalignment object is created by MakePHOSFullMisalignment.C. It reads survey table (ascii file) and creates alignment objects. • Misalignment is overlaps-free: fiducial gaps between modules were enough for displacements. PHOS structures (cradle, wheels, rails were not surveyed and moved coherently to avoid overlaps. • PHOS alignment is used in reconstruction. PHOS offline status

  20. Todo list for the nearest future • Further calibration improvement: the goal to achieve 3% decalibration • Bad channel map refining • Raw spectrum fitting • QA checker implementation • QA reference data • Improvement in PHSQA AMORE agent • TRU (fake ALTRO) data decoding • PHOS L0 trigger configuration and input to CTP PHOS offline status

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