Transcript Level 1 Simulation: Status and Planning

CAL CALIBRATION
Overview and Stability
Thomas Schörner-Sadenius
Hamburg University
ESCALE Meeting
DESY, 7 June 2005
INTRODUCTION TO THE ZEUS UCAL
Depleted Uranium for calibration and compensation
Principle
Depleted Uranium – scintillator calorimeter; analog pipelined
PMT readout. Analog electronics on front-end cards on detector;
digital electronics in 3rd floor of rucksack.
Division in F/B/RCAL with 2172/2592/1154 cells, 2 PMTs per cell
EM cell size: 520 (1020) cm2 in F/BCAL (RCAL)
HA cell size: 2020 cm2.
Calibration
Resolution: (e)/E=17%/E, (h)/E=35%/E
Claim: absolute energy scale known to 1%.
Uranium
98.1% 238U,  decay to
 cascades in between.
234Th,
 decays to
234PA
and then
234U,
Emax()=2.3 MeV, E()=10-1000keV
(U)=4.5 Gy (Giga-years)  rather stable signal of ZEUS lifetime.
Idea
DESY 7 June 2005
Use UNO (Uranium noise) signal to monitor CAL behaviour with time
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READOUT OVERVIEW
Necessary for understanding of calibration constants.
20ms integration time over UNO current
IUNO
shaper
pipeline
buffer
Qhigh
shaper
pipeline
buffer
Qlow
PMT
UNO
To trigger
Digital
electronics
VDAC
Vref
DAC
Vref=1.67V
55pC
Energy Q
Current IPMT
Charge Q
Voltage V
ADC counts
Necessary: Calibration of particle/jet energy to ADC counts
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CALIBRATION IDEA
Use stable Uranium noise as calibration signal
Assumption 1
Uranium activity stable in time.
Assumption 2
UNO signal stable in time to about 1% (CERN testbeam)
Assumption 3
e/UNO or h/UNO for given Ee, Eh stable in time (studying the
ratio cancels some uncertainties  more precise result
Assumption 4
e,h response linear in energy (CERN testbeam)
STEP A
STEP B
Keep UNO signal stable
 trimming of HV settings
 UNO scale factors (offline GAFs)
From known and linear e/UNO (h/UNO)
then estimate energy of e,h.
One of the many complications:
DESY 7 June 2005
• UNO[ADC] fixed
• e(E)[ADC]/UNO[ADC]: CERN!
• then e[ADC]e[GeV]
UNO signal and (fast) physics signal go through different
signal paths on front-end card!
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“1%” CALIBRATION
Refers to rather different things
1% - the first
Intermodule/interregion calibration
After UNO calibration: compare various modules in their
response to well-defined input energies (test beam)
 spread of various modules ~ 1%
1% - the second
Determination of absolute scale
E(particle)  ADC: after UNO calibration (UNO
gives precise ADC count):
particle_ signal
absolute scale delivered by
UNO _ signal
(using the test beam results):
‘one-to-one relation between
ADC and energy. Within one
module response from towers
is gaussian with width ~1%!
 in testbeam fix scale to 1%!
Two important questions/tasks here:
-- Keep the UNO signal to the nominal as closely as possible (UNO scale factors,
but also other smaller corrections for front-end, signal path etc.)
-- Derive offline correction factors from physics data (kin. Peak, E-pz, etc.)
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UNO SCALE FACTORS
CAL offline GAFs – the one that always stop the reconstruction
For all CAL regions
means within few
permille around 1.
Widths below 1%.
Channel-by-channel comparison of two UNO GAFs
from 010305 and 080505.
Means ~1permille.
Widths ~0.5%.
Several HV adjustments
between the two dates.
No systematic trends,
distributions gaussian 
absolute calibration
preserved at 1%-level!
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UNO SCALE FACTORS
Module by Module comparisons of relative UNO differences
No significant changes between modules  intermodule calibration still at 1%-level!
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FURTHER OFFLINE CORRECTIONS
Motivated by physics; take into account dead material etc.
PHANTOM routine escale03.fpp (default in ORANGE) applies corrections
for F/B/RCAL, separately for EMC and HAC;
in addition cell corrections for some RCAL cells
FEMC: 1.024
FHAC: 0.941
BEMC: 1.003*1.05
BHAC: 1.044*1.05
REMC: 1.022
RHAC: 1.022
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Corrections derived from kinematic peak
events and DA measurements.
-- repeat in newer data?
-- dependence on physics case?
-- any manpower currently involved?
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SUMMARY
and possible outlook
Started to look into long-term stability of CAL calibration (UNO scale factors).
 absolute calibration seems stable to within 1% over time.
 intermodule calibration within about 1%
 if initial absolute energy calibration good to 1%, then this quality
is probably preserved until today.
Needed: Better understand of calibration in detail; only then can judge on
quality of calibration.
Important:
 control of offline CAL regional (caltru) correction factors
 use physics events for that (kin. peak, E-pz, DA method etc.)
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