1. EZDC spectra reconstruction and calibration1 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, November 2003

2. 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

3. 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

4. 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

5. 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

6. 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)

7. NA60 In2003 – Run selection for ZDC calibration – 1

8. 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 

9. 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%

10. 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

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

12. 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 ~ I = 1.0•107 ions/burst
e ~ I = 3.5•107 ions/burst
e ~ I = 5.0•107 ions/burst
e ~ I = 5.5•107 ions/burst

13. 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)