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Preshower calibration

Preshower calibration. S. Monteil, K. Sobczak 1/09/2010. Current status. Current status. A short reminder of the method: A distribution of ADC counts for tracks pointing towards a cell. Corrections for particle track length in side the cell applied.

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Preshower calibration

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  1. Preshower calibration S. Monteil, K. Sobczak 1/09/2010 PRS calibration

  2. Current status PRS calibration

  3. Current status • A short reminder of the method: • A distribution of ADC counts for tracks pointing towards a cell. Corrections for particle track length inside the cell applied. • Fit by a convolution of Landau and Gaussian. MIP position is the most probable value of Landau. • Uniformization inside boards with numeric gains (range [1,2]) and between boards with HV settings. First 2010 april data PRS calibration

  4. Current status Is the detector calibrated? - It depends... • The last calibration was applied on 02/03/2010 using 2009 data (MIP position at 15 ADC counts). • The detector is not uniformized (plots below): • 10% calibration inside regions, • the difference between middle and outer is 9% for the A side and 7% for the C side, • the difference between inner and outer is 16% for the A side and 12% for the C side. • Corrective factors obtained in April applied into the software (thanks to Olivier). • Calibration performance proved by energy flow method (thanks to Aurelien, the next slide is from his presentation in April) at the ~5% level. Detector point of view: no Software point of view: yes What can be improved? PRS calibration

  5. 2010 real data : EFlow vs Landau The Mip calibration is ”contained” in the EF calibration which intrinsic precision is 5%. Correlation of the coefficients extracted from the EFlow using MagOff data (x-axis) and the Landau fit (y-axis) given by Stephane. Inner A Middle A Outer A ρ = 77% ρ = 70% ρ = 54% Inner C Middle C Outer C ρ = 64% ρ = 59% ρ = 58% X and Y axis are in units of standard deviations. PRS calibration A. MARTENS – Calorimeter WG meeting - 22/04/2010

  6. Current status What is the precision of the current software calibration? Take May data as an example, split by BXID. [MPV(meas)-MPV(average)]/MPV(meas.) PRS calibration

  7. Current status Same for odd. [MPV(meas)-MPV(average)]/MPV(meas.) PRS calibration

  8. Current status • Lessons from this exercise: • Distributions of the spread of the channels are basically gaussian. • Even BXID are software calibrated at the 5% level (68 % of the channels have the same answer within ±5%). • Odd BXID are software calibrated at the 10% (see later for the difference). • Systematic shift between odd and even BXID at the 10 % level at maximum. PRS calibration

  9. Motivation for a recalibration (reminder) We want the detector calibrated for the EM triggers: the same threshold ( > 100 ADC counts) is applied at the trigger level. PRS calibration

  10. Refined analysis PRS calibration

  11. Refined analysis • To improve the precision of the calibration following changes to the fitting procedure were done (since the last software corrections were applied): • De-gain distribution before fitting to remove empty bins from histograms. Apply track length correction after. • Added exponential distribution for a pedestal background shape. Final fitting model: Landau × Gaussian + exponential. • Split in even / odd BXID. It should account for different VFE electronics gain and different pedestals. • Evaluated on a sample from April and checked on a sample essentially from May (r4s5 w/ April data excluded). • Latest data are currently under analysis. • Legend for the next slides: • Current sw calibration – previous calibration (old model) which is currently inside the software and which is used for the reconstruction. • April – the same sample as the sample used for current sw calibration , fit with the new model, split even/odd. • r4s5 – sample mostly from May, fit with new model used as a reference for checks, split even/odd. PRS calibration

  12. The improved fit result by regions The differences between even and odd, between both of them and the previous calibration (currently in software) are presented on the next slides. PRS calibration

  13. Comparison even / odd PRS calibration

  14. Comparison even / odd • The MPV values for even and odd BXID are not the same with an average shiftand RMS given on the plots. • Typically MPV values from even BXID sample are greater than from odd BXID sample. PRS calibration

  15. Even / odd comparison by regions • The difference between even and odd MPV value is higher in some regions especially for: • PRS 2, • PRS 7 crates 11 - 13. • Pedestal measurement related ? Under investigation. • Excluded channels don’t contain a MIP shaped signal (an example later). PRS calibration

  16. Comparison with the current calibration PRS calibration

  17. Even / odd comparison with current software calibration Odd • Odd sample has a larger spread (related to the fraction of odd and even in the initial calibration sample. • Shifts of the mean values towards negative values are related to the model. Even PRS calibration

  18. Even / odd comparison with current software calibration • Correlation between split determination and averaged one (as in current sw). • 2/3 of the events were in even BX. PRS calibration

  19. Detector stability. Comparison with May sample (r4s5). PRS calibration

  20. Comparison with May sample (r4s5): Detector stability • Odd BXID:Shift not greater than 0.1%.RMS not greater than 0.5%. • Even BXID:Positive shift of the mean value of MPV but still no more than 1%.RMS no more than 1.5%. • It is still below 5%. • The exact source of the difference is yet to be found (one but possibly not the only one is the statistics used). PRS calibration

  21. Comparison with May sample (r4s5): Detector stability • The comparison shows the correlations between the samples from April and from May (r4s5) are grater than 99% except of even BXID A side Middle sample which is 97%. • It allows to conclude that the detector was very satisfactorily stable in terms of gains and pedestals during that period (and timing). PRS calibration

  22. Open questions and known issues. PRS calibration

  23. Open questions and known issues • Still a few questions to answer (but within 5% calibration!) • Even/odd difference: time stability plots. • Pedestal plots have to be investigated. • Terrible channels • Dead channels ( 2 ) PRS 7 FEB 7– almost no statistics Reference neighbor PRS calibration

  24. Open questions and known issues • 16 channels + 3: no MIP shape ( a 1/4 board faulty - board to be replaced ) – Excluded channels on 2D plots. Reference neighbor • They do correspond to 2 ADCs. Intermittent errors. Misadjusted sampling or hw failures ? • Uncorrectable pedestals (~20 channels). Pedestal 3627 PRS calibration

  25. Open questions • Untypical shapes (~20 channels). • Some boards with higher difference between even and odd. • Correlation of spotted „bad” channels with the EF was done once. Basically all problems spotted by the EF were identified. It might be worth to make a second pass with the latest data. PRS calibration

  26. Summary and plans PRS calibration

  27. Summary • PRS is currently calibrated at the ~5% level. • Still, this is software calibration. The detector itself is ~15%. The EM triggers are not benefitting from the 5% calibration. • A refined determination of the MIP position has been developped. Older results are reproduced. • Calibration is split according to the BXID alternance to account for the different gains of the VFE electronics subchannels (and pedestal differences). • Differences up to 10 % between odd and even BXID are observed. • Still open questions here and there. PRS calibration

  28. Plans • Corrections by subchannels are ready for the numeric gains to be set in the FE electronics. • HV settings to uniformize tubes are accordingly ready (provided the last checks are completed). • We’d like to calibrate the detector at the next possible occasion. • Latest data from the summer still to be analyzed. PRS calibration

  29. Backup PRS calibration

  30. Even / odd comparison with current software calibration • Current calibration is closer to even MPV valuesthan to odd MPV values because the sample used to obtain it had a ratio of even / odd BXID events ≈ 3:2. PRS calibration

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