EZDC spectra reconstruction and calibration 1 2 3 4 Description of the reconstruction methods Analysis of the ZDC “In-Time” and “Out-Of-Time” ADC channels correlation Pedestal calculation and subtraction Energy calibration Oct 2003 run selection for pedestal calibration First results of calibration na60ZDCCalib data production Alberto Colla NA60 collaboration meeting Cern, 25-27 November 2003

ZDC signal baseline subtraction baseline oscillation due to external electronic noise  frequency 50 Hz; amplitude ~100 mV coupling of each ZDC “In-Time” channel with an “Out-Of-Time” one laser trigger event selection to get the correlation between In-Time and Out-of-Time channels linear fit of correlation plot Subtraction of the ADC In-time pedestal using the Out-Of-Time value and the correlation function 4 ms 20 mV Out-of-Time ADC gate In-Time ADC gate physics run ~ 20 ns ~ 1 V High intensity acquisition  high probability of signals in the OOT gate extension of the correlation analysis to all the combinations ITi vs OOTk gates 4 ZDC towers + 4 OOT gates  16 correlations

In-Time vs Out-Of-Time correlation analysis -1 during correlation filling: skip of Laser trigger event if previous event was Laser trigger  avoid “out of burst” correlation “Cleaning” of correlations to reject pedestal events with signals in the ADC gates  the bins of the correlation histograms which have contents lower than 1/10 of the maximum bin content are set to zero Out-Of-Time ADC In-Time ADC signal in the ADC gates In-Time ADC Out-Of-Time ADC “good” correlation

In-Time vs Out-Of-Time correlation analysis -2 projection of the “cleaned” correlation on the OOT axis gaussian fit to the projected spectrum  obtain the range of the linear fit to the correlation OOT Laser trigger spectrum OOT Projection of “cleaned” correlation Range of the linear fit to the correlations OOT 2 ADC OOT 1 ADC

In-Time vs Out-Of-Time correlation analysis -3 OOT 1 OOT 2 OOT 3 OOT 4 IT 1 creation of a profile histogram from the cleaned correlation linear fit to the profile histogram the 2 parameters of the fitting function are set in the calibration file

ZDC energy calibration from raw data… ZDC Energy Spectrum pedestal subtraction Fit of the non-interacting ion peak position in the adc spectrum to obtain the energy calibration coefficient obtain calibrated spectra non interacting In ions peak ZDC spectrum (ADC ch) ZDC ADC Spectrum interaction spectrum EZDC (GeV)

NA60 In2003 – Run selection for ZDC calibration – 1

NA60 In2003 – Run selection for ZDC calibration – 2 Calibration data already available 1 2 3 4 -5 5mm -5mm 5 PT7 = -900A PT7 = +900A periods selected accordingly to the behavior of the on-line monitored EZDC spectrum and to the settings on PT7 magnet and Quartz Blade reminder… from on-line monitoring: position of the ZDC signal centroid 

Pedestal subtraction methods 2 pedestal subtraction methods have been tested so far: “BestCorr” Calculation of the pedestal of the 4 ZDC towers signals from the Out-Of-Time ADC signal “closest” to the mean value of the Laser trigger distribution “BestCorr+PCO” Same as 1), but if all of the 4 Out-Of-Time ADC signals are larger than an upper limit (calculated from the Laser trigger OOT distributions) the pedestal is subtracted using the mean value of the Laser trigger spectra Upper limit for “BestCorr+PCO” Pedestal subtraction OOT 1 ADC OOT Laser trigger spectrum OOT Projection of “cleaned” correlation The two pedestal subtraction methods give the same results BestCorr+PCO: mean value utilization for pedestal subtraction < 0.2%

Pedestal subtraction – Test with low intensity spectra calibration methods tested using data from low intensity (I=107 ions/burst) runs Low intensity run High intensity run EZDC (GeV) BestCorr method Pile-Up spectrum

EZDC calibrated Spectra – PT7 = ± 900A comparison sum of the EZDC spectra of the already calibrated runs PT7 = +900A PT7 = -900A EZDC (GeV) EZDC (GeV)

EZDC calibrated Spectra – PT7 = ± 900A comparison - 2 EZDC distributions in very good agreement  good uniformity of the ZDC response! EZDC (GeV) PT7 = -900A PT7 = +900A Comment on ZDC energy resolution e resolution worsens with beam intensity: e ~ 10% @ I = 1.0•107 ions/burst e ~ 11% @ I = 3.5•107 ions/burst e ~ 12% @ I = 5.0•107 ions/burst e ~ 13% @ I = 5.5•107 ions/burst

conclusions Calibration files: production on way “first release” of calibrated data to be expected for December 10th (as scheduled yesterday) Calibration data will include:  parameters for ZDC, Quartz Blade and Pile-Up pedestal subtraction  ZDC and QB calibration coefficients  parameters for QB corrections (signal behavior with time due to radiation damage) parallel work:  check of ZDC spectrum behavior in each sub-period  other methods for pedestal subtraction will be tested:  utilization of the Pile-Up ADC gates which are “far” from the triggered signal (and behave like Out-Of-Time gates)