Transcript EM CAL calibration

GLAST LAT Project
CAL Software Workshop
EM CAL Calibration
Xin Chen, Eduardo
X. Chen
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GLAST LAT Project
CAL Software Workshop
Outline
• Generate CAL calibration constants used for reconstruction
– Pedestal
– Light asymmetry
– Electronics gain (MeV/ADC)
• VDG photon energy spectrum after calibration
• Light taper study, currently not used in reconstruction
• Conclusion and future plans
X. Chen
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GLAST LAT Project
CAL Software Workshop
Software infrastructure
•
Based on Sasha’s scripts, a calibGenCAL package is written to do the
calibrations:
– It uses CMT to set up environment variables and dependences on
ROOT I/O libraries. By this way, it is also version controlled.
– It builds an executable and takes input parameters from a job
option file. Thus multiple jobs can be easily submitted to the batch
to process very large amount of data in a short time.
•
Light taper study is also done in the calibGenCAL package.
•
Some codes also exist to do the trending analyses.
X. Chen
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GLAST LAT Project
CAL Software Workshop
EM data used to do the calibrations
From Sep 28th to Oct 12th, two cosmic runs per day (~ 4 hours) were used to
produce calibration Constants for the calorimeter
Date
Run type
Trigger
Sep 27 – Oct 1, 2003
Cosmic
CAL_LO
Oct 2 – Oct 5, 2003
Cosmic
External
Oct 6 – Oct 8, 2003
VDG
3 in a row / CAL_LO
Oct 9 – Oct 12, 2003
Cosmic
External
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GLAST LAT Project
CAL Software Workshop
Raw ADC distribution for layer 0, column 6, end 0, range 0
Data taken on Sep 27th, 2003
Pedestal
Muon peak
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GLAST LAT Project
CAL Software Workshop
Light asymmetry = Log ( ADC(pos) / ADC(neg) )
Slope is the calibrated attenuation length
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GLAST LAT Project
CAL Software Workshop
Muon peak distribution for layer 0, column 6, end 0, range 0
Data taken on Sep 27th, 2003
1 MIP = 12.3 MeV
X. Chen
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GLAST LAT Project
CAL Software Workshop
Time Dependence Estimate
• Within 16 days:
– Changes in pedestal are less than 0.8%
• ~ 10000 events used in the fitting
– Changes in attenuation length are less than 5%
• ~ 900 events used in the fitting
– Changes in muon peak are less than 4%
• ~ 500 events used in the fitting
• No significant time dependence. May need to process more
events to achieve better accuracy
– Is this desirable considering the efforts?
X. Chen
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GLAST LAT Project
CAL Software Workshop
VDG photons on EM
Cosmic Background
CAL
X. Chen
TKR
66% 17.6 MeV, 34% 14.6 MeV
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GLAST LAT Project
CAL Software Workshop
Raw ADC distribution for all crystals
No of entries
Without calibrations
Cosmic: ebf031009105206
pedestal
muon
Raw ADC counts
X. Chen
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GLAST LAT Project
CAL Software Workshop
Calibrated energy for all crystals, zDir < -0.9
Two runs are normalized by the run time
VDG+Cosmic: ebf031007191651
Cosmic: ebf031009105206
Pedestal
VDG events
Muon peak
(MeV)
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GLAST LAT Project
CAL Software Workshop
Calculate total energy deposited in CAL
• Require at least 1 crystal has deposited energy > 4MeV
– Remove almost all of noises
• Sum only the largest 12 deposited energies in crystals
• Only use events going along the z axis of the tracker
(zDir < -0.9) to avoid path length dependence
X. Chen
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GLAST LAT Project
CAL Software Workshop
Energy spectrum
Two runs are normalized by the run time
Number of events
VDG+Cosmic: ebf031007191651
Cosmic: ebf031009105206
“Photon”
Muon
calEnergy*(-zDir) (MeV)
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GLAST LAT Project
CAL Software Workshop
Light Tapering Method
• Use EM data to study position dependence of muon signals in
each crystal
– Extrapolate muon track reconstructed by the tracker to
determine the position where the muon passes through
crystals
– Divide each crystal into number of bins (e.g. 40)
– Accumulate muon signals in each bin
– Do a landau fit for each bin to get the muon peak position
(pedestal subtracted but not gain corrected)
– Make a muon peak vs. position plot for each crystal
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GLAST LAT Project
CAL Software Workshop
EM data used in the light taper analyses
• All EM data taken between Oct 2 and Oct 13, 2003.
– Externally triggered
– With Pb beneath the EM to reject low energy cosmic rays
– ~ 69 runs, ~ 1.6 million triggers
– Run list can be found at:
http://www-glast.slac.stanford.edu/IntegrationTest/SVAC/EM/ruinfo.htm
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GLAST LAT Project
CAL Software Workshop
Muon peak vs. position in a crystal
counts
ADC
corrected
Pedestal
counts
ADC
corrected
Pedestal
layer 0, col 5 (8mm bin size)
Negative end signal
Positive end signal
Position along the crystal (mm)
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GLAST LAT Project
CAL Software Workshop
Muon peak vs. position in a crystal
Pedestal corrected ADC counts
layer 0, col 5 (3mm bin size)
Negative end signal
Positive end signal
Position along the crystal (mm)
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GLAST LAT Project
CAL Software Workshop
Conclusion
• Codes have been written and tested to produce calibration
constants for CAL.
• With calibration constants, energy spectra of VDG and cosmic
signals make senses
• There does not seem to be any significant time dependences
of the calibration constants for CAL
• Codes also exist to do the light taper study. Need discussion
how to proceed with the light taper study? Does the
reconstruction need inputs from the light taper study? If so, in
what format?
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GLAST LAT Project
CAL Software Workshop
Future Plan
• After the CAL group delivers finalized codes to do the
calibration, we need to re-exercise the full calibration and data
analyses chain.
• We are developing codes to store calibration constants in
oracle database and a web application to do the trending
analyses on the constants. We plan to have a meeting in three
weeks’ time.
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GLAST LAT Project
CAL Software Workshop
VDG photons on EM
Cosmic Background
TKR
66% 17.6 MeV, 34% 14.6 MeV
CAL
X. Chen
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GLAST LAT Project
CAL Software Workshop
Energy spectrum
EM is vertically placed, photons come from side of CAL
Number of events
VDG+Cosmic: ebf031008000405
Photon
Muon
calEnergy (MeV)
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GLAST LAT Project
CAL Software Workshop
No of channels
Changes in light attenuation length
2*(Slope928-Slope929)/(Slope928+Slope929)
No of channels
Slope change
2*(Slope928-Slope1001)/(Slope928+Slope1001)
No of channels
Slope change
2*(Slope928-Slope1005)/(Slope928+Slope1005)
No of channels
Slope change
2*(Slope928-Slope1012)/(Slope928+Slope1012)
X. Chen
Slope change
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GLAST LAT Project
CAL Software Workshop
No of channels
Changes in muon peak
2*(Peak928-Peak929)/(Peak928+Peak929)
No of channels
Peak change
2*(Peak928-Peak1001)/(Peak928+Peak1001)
No of channels
Peak change
2*(Peak928-Peak1005)/(Peak928+Peak1005)
No of channels
Peak change
2*(Peak928-Peak1012)/(Peak928+Peak1012)
X. Chen
Peak change
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