1. 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)
July 17,2008
ALICE EMCal Beam test

2. CERN SPS and PS Tests 2007 Goals: Calibration with Cosmics
Quantify how well it will work by comparison to electron calibration
Determine best procedure
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
July 17,2008
ALICE EMCal Beam test

3. EMCal Test Setup - CERN 2007 Z=0 configuration
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
July 17,2008
ALICE EMCal Beam test

4. EMCal Test Setup - CERN 2007 Large Z configuration July 17,2008
ALICE EMCal Beam test

5. EMCal Test Setup - CERN 2007 Phi-Tilt configurations - 3,6,9o
July 17,2008
ALICE EMCal Beam test

6. 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
July 17,2008
ALICE EMCal Beam test

7. 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.
July 17,2008
ALICE EMCal Beam test

8. LED Gain Monitoring 8x8 towers FADC time spectra
LED Driver with fiber distribution gives ~30 GeV equivalent. Ideally, would like GeV to be at upper range of High Gain -> good signal on high and low gain.
LED system gives enough light!
July 17,2008
ALICE EMCal Beam test

9. Understanding Gain(T) Corrections
SPS1 SPS2 PS
Temperature measurements inside each strip module (day/night variations clearly seen)
Does the LED system track these Temperature variations?
Gain variation ~2% / oC
1o C
July 17,2008
ALICE EMCal Beam test

10. 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
July 17,2008
ALICE EMCal Beam test

11. 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.
July 17,2008
ALICE EMCal Beam test

12. 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!
July 17,2008
ALICE EMCal Beam test

13. 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
July 17,2008
ALICE EMCal Beam test

14. PS Setup
July 17,2008
ALICE EMCal Beam test

15. 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
July 17,2008
ALICE EMCal Beam test

16. 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.
July 17,2008
ALICE EMCal Beam test

17. 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%.
We need to demonstrate that we can do this with a cosmic trigger setup for the initial calibration of the SMs.
Cosmics result - Sebastien, Aleksei
MIP peak
MIP peak variation
1.5%
From Aleksei Pavlinov
July 17,2008
ALICE EMCal Beam test

18. 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
for details for analysis:
Run logbooks and Elogs for SPS, PS, and cosmics periods
Pointers to analysis code to begin analysis
July 17,2008
ALICE EMCal Beam test

19. 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 bi-weekly 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
July 17,2008
ALICE EMCal Beam test

20. Calibration , 80 GeV, SPS1 – 3 xlog:ylog distribution of the cluster
Position scan:
Beam distribution for
various runs
This and following Slides from Aleksei:

21. Calibration , 80 GeV, SPS1 – 4 Best and worst runs for resolution

22. 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

23. 60 GeV - 1 1. Mean value of beam energy is almost the same
as “ideal” one
(only reconstruction here – no calibration)‏

24. 5GEV - 1
Mean value of beam energy is the same
as “ideal” one <1%

25. 5GEV – 2 Resolution varies from 6.8% to 7.6%
Reconstructed beam energy has RMS ~1.%