CERN SPS and PS Tests 2007
Goals:
• Show we have a working EMCal system
– That meets specifications!
• Quantify the performance characteristics of production EMCal
– Energy resolution
– Position resolution
– Electron/hadron discrimination by shower shape
– Time measurement?
– Dependence of all of above on position of incidence uniformity
• Demonstrate we have a working gain monitoring system (LED)
– Sufficient signal to be useful
– Stable and reproducible LED signal in each tower
• Does LED variation track gain variations? (e.g.due to temperature)
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CERN SPS and PS Tests 2007
Goals:
• Calibration with Cosmics
– Quantify how well it will work by comparison to electron calibration
– Determine best procedure
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• Trigger - data rate
• Zero suppression? (data volume problem)
• Analysis method - single tower, isolation cut, cluster?
Data set to develop and test analysis software
– Optimal E-signal extraction (speed vs performance)
– Gain variation corrections using LED or Temperature data
– Clustering
– Shower identification cuts
– Refine simulated data parameters (noise, shower tracking cuts)
Exercise EMCal “system” in ALICE
– PVSS control
– DATE data acquisition
– Storage and access to “large” data sets in CASTOR & AliEn
– Batch production of ESD
– Analyisis within ALICE offline framework
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EMCal Test Setup - CERN 2007
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•
•
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Pre-Production Modules (1/3 size “strip modules”)
4x4 modules or 8x8 towers
Readout with production version of all components (FEE v1.1e) (except IPCB and
GTL bus, no TRU)
Readout via ALICE DAQ - DATE, stored in CASTOR (eventually).
~3.5m
Z=0 configuration
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EMCal Test Setup - CERN 2007
Large Z configuration
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EMCal Test Setup - CERN 2007
Phi-Tilt configurations - 3,6,9o
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Strip Module Internal Components
Production versions of internal components: APD+Preamplifier, Transition
Card, LED fiber distribution, Temperature sensors, molex cables
2007
Prototype
Modules
Transition Card
Temperature measurements inside strip modules
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EMCal LED Gain Monitoring System
• LED system needed for gain
adjustment and gain
monitoring.
• LED system used for FNAL
tests was N.G.
• One fiber per module
(shown) excites WLS bundle
- low efficiency.
• 12 modules (fibers) per strip
module fed by one fiber
from remote LED to strip
module.
• Prototype LED driver used in
test beam.
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LED Gain Monitoring
8x8 towers FADC time spectra
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•
LED Driver with fiber distribution gives ~30 GeV equivalent. Ideally, would
like LED @~13 GeV to be at upper range of High Gain -> good signal on high
and low gain.
LED system gives enough light!
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Understanding Gain(T) Corrections
Temperature measurements
inside each strip module
(day/night variations clearly
seen)
SPS1 SPS2 PS
Does the LED system track
these Temperature
variations?
1o C
Gain variation ~2% / oC
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SPS Measurements
• Tertiary beam.
– By choice of secondary target and absorber obtained very pure
electron or hadron beam
• Simple scintillator trigger - no need for cerenkov for particle ID
• MWPC tracking: 3MWPC (Grenoble) + 1 MWPC (CERN)
– EMCal position resolution and uniformity (multiple planes allow to
determine tracking residuals to extract EMCal only resolution)
– Took electron data at 5,10,20,40,60,80 and 100 GeV/c
– Took hadron data at 20,40,60,80 and 100 GeV/c
– Scanned through all towers with 80 GeV/c electrons for relative
gain calibration - twice (check reproducibility)
– Scanned through most towers with 80 GeV/c hadrons to
compare MIP vs electron calibration
– Position scans to check uniformity
– Geometry: Z=0 and large Z geometries, and 6 and 9 degrees phi
incidence
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Electron Event at SPS
FEC 5
FEC 6
Event Display;
ADC vs Time-Sample
#.
80 GeV electron event
Relative gain
calibration:
position scan with 80
GeV/c electrons in
each tower.
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Example energy distributions
3x3 tower sums
With preliminary SPS calibrations (by
Marco, Aleksei).
In general, ~20% more light - as
expected by increased sampling.
Note the “clean” e spectra!
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Resolution vs Energy
Momentum scans:
5,10,20,40,60,80 and 100
GeV/c electrons at several
central locations and across
boundaries.
Preliminary energy
resolution better than with
first prototypes - better
sampling
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PS Setup
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PS Measurements
• Secondary beam.
– Beam trigger based on Scintillators
– Cerenkov counter to tag electrons, electron trigger
– Muon veto paddle to tag muons for beam triggers
– MWPC tracking: 2MWPC (Grenoble)
– Took electron data at 0.5, 1,2,3,5 and 6.5 GeV/c
– Took beam data at 0.5, 1,2,3,5 and 6.5 GeV/c GeV/c
– Scanned through all towers (twice) with 3 GeV/c electrons for
relative gain calibration.
– Scanned through all towers with 3 GeV/c hadrons to compare
MIP vs electron calibration
– Position scans to check uniformity
– Geometry: Z=0 and large Z geometries, and 3, 6 and 9 degrees
phi incidence;
– laid strip module on side and scanned with hadrons through “top”
to check as a possible cosmics configuration
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Cosmics calibration test at CERN
Some Cosmics data was been taken:
• Data with:
•Testbeam gains
•Matched gains
•Maximum bias
• Different scint. trigger conditions
• Okay - but more difficult than sim.
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Precision of “Cosmics” calibration
• FNAL test beam results:
After calibration of towers
with electron beam (16
GeV/c) position of “MIP”
peak for each tower
observed to vary by less
than +/-1.5%.
MIP peak
• We need to demonstrate
that we can do this with a
cosmic trigger setup for the
initial calibration of the
SMs.
MIP peak variation
• Cosmics result - Sebastien,
Aleksei
1.5%
From Aleksei Pavlinov
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Analysis
• We have a very large data set
– More than 1100 runs, 525 Gbytes of data from SPS+PS
– A similarly large amount from the Cosmics setup
• The raw data volume is sufficiently large that the only copy is in
CERN central storage.
• Early attempts (by David) to process the data via AliEn were very
frustrating - (staging delays causing processes to abort)
• The raw->ESD processing task is sufficiently large that the ALICE
offline group has volunteered that they will manage the offline
production for us - to David’s delight!
– We likely will want to repeat this to test “improvements” in the raw
data peak extraction
• See David’s nice documentation at
http://dsilverm.web.cern.ch/dsilverm/testbeam07
for details for analysis:
– Run logbooks and Elogs for SPS, PS, and cosmics periods
– Pointers to analysis code to begin analysis
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Analysis - Status: “Disorganized”
• We had/have a large number of people interested to analyze data
(Grenoble, Nantes, Catania, Frascati, CERN, WSU, Houston,
Tennessee), but many without EMCal experience.
• Analysis task list (~NIM figures) with volunteers
• We had semi-regular analysis meetings for a short while after the
beam test, but they stopped with results being reported in the biweekly offline meeting
– Useful, but lost focus and direction
• Three main General tasks needed to before final analyses:
– Gain(Temperature) correction result and tools
• Done - Rachid, David, (Aleksei on his own)
– Tracking data with MWPCs (for all position studies)
• Almost done - Josh, Dilan, David
– Final Raw->ESD production with optmized signal peak fitting
• Soon - Raphaelle, ALICE Offline group
• Need to resume regular dedicated Testbeam analysis meetings…
• Ultimate goals:
– Confirm Cosmics calibration procedure
– NIM paper
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Calibration , 80 GeV, SPS1 – 3
xlog:ylog distribution of the cluster
Position scan:
Beam distribution for
various runs
This and following Slides from Aleksei:
Calibration , 80 GeV, SPS1 – 4
Best and worst runs for resolution
Resolution ~1.7%
Resolution ~2.4%
Calibration , 80 GeV, SPS1 – 5
Summary picture – E(rec) vs #runs
Resolution varies from 1.6% to 2.4%
 Reconstructed beam energy has RMS ~1%
 Set of calibration coefficients are using for reconstruction

60 GeV - 1
1. Mean value of beam energy is almost the same
as “ideal” one
(only reconstruction here – no calibration)
5GEV - 1
Mean value of beam energy is the same
as “ideal” one <1%
5GEV – 2
Resolution varies from 6.8% to 7.6%
 Reconstructed beam energy has RMS ~1.%
