1. COMPASS calorimeters S. Platchkov IRFU, CEA-Saclay GDR, 8-9 avril 2008
SP; Apr. 8, 2007
GDR Nucleon

2. Outlook The COMPASS calorimeters
Calibration issues – T9 test beam results
Monitoring – laser upgrade
The DVCS project – ECAL0 calorimeter
SP; Apr. 8, 2007
GDR Nucleon

3. COMPASS set-up
SP; Apr. 8, 2007
GDR Nucleon

4. ECAL1 OLGA MAINZ GAMS Electronics for all: 320 blocks (143x143 mm2)
SADC
291
400
SP; Apr. 8, 2007
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5. ECAL2 Matrix: 64 x 48 blocks with 10 x 10 central hole
2972 channels (all are Lead Glass GAMS blocks)
Electronics:
FIADCs
SADCs
SADC
FIADC
183
SADC
244
SP; Apr. 8, 2007
GDR Nucleon

6. COMPASS LG blocks properties
SP; Apr. 8, 2007
GDR Nucleon

7. Calibration issues
SP; Apr. 8, 2007
GDR Nucleon

8. Calibration of ECALs (during µ runs)
Energy range: ~5 GeV – 50 GeV
Use SPS 40 GeV electron beam (~few 103/spill)
Two-step procedure:
1. Use e- to measure ADC peak values. Change HVs accordingly
2. Use e- a second time for fine tuning. Use the resulting correction factors for energy measurements.
ECAL1
Energy range: ~1 GeV – 10 GeV
Use halo muons (no e- beam of low enough energy)
Refine the procedure at the CERN-T9 test beam facility
SP; Apr. 8, 2007
GDR Nucleon

9. T9 test beam set-up (CERN, October 2007)
Energy: 1 – 15 GeV Beam: p, µ, e-
Scintillator
counters
Scintillator hodoscope
RichWall prototype
HCAL2
3x3 modules
Cherenkov counters
ECAL modules:
Shashlik 5x5
GAMS 5x5, Mainz 3x2, Olga 2x2
SP; Apr. 8, 2007
GDR Nucleon

10. T9 set-up
SP; Apr. 8, 2007
GDR Nucleon

11. Calibration procedure
First step (relative, or inter-calibration)
Beam centered at each cell
Assume all beam energy is deposited in the same block
For electrons
For muons
Second step (absolute calibration)
Sum of 9 or 25 blocks (all the deposited energy):
Rescale:
SP; Apr. 8, 2007
GDR Nucleon

12. SADC spectra after muon intercalibration
SP; Apr. 8, 2007
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13. Calibration using muon “MIP” energy
Mean = /
 MIP energy: 0.7 GeV
SP; Apr. 8, 2007
GDR Nucleon

14. Final calibration using e- beam energy
MPV = /
MIP energy: ~10% underestimated or wrong assumption?
SP; Apr. 8, 2007
GDR Nucleon

15. Muon “energy losses” in PbO modules
How large is the muon “MIP” loss in PbO ?
Measured: Eµ = 620 MeV
Calc:
Calculated: Eµ = 280 MeV !!
 620/280 ≈ 2.2 !!
But also: differences as a function of the energy:
Differences between -10 and +1% !
SP; Apr. 8, 2007
GDR Nucleon

16. Muon “energy losses”: Cherenkov photons from muons:
from 1) Ionization, 2) Cherenkov radiation
Ionization loss Eion : energy dependence in PbO
Eion( 1 GeV) = 1.40 g-1cm2 x 45 cm x 3.86 g.cm-3 = 243 MeV
Eion( 4 GeV) = 1.63 g-1cm2 x 45 cm x 3.86 g.cm-3 = 283 MeV
Eion(10 GeV) = 1.81 g-1cm2 x 45 cm x 3.86 g.cm-3 = 314 MeV
Difference = 71 MeV (~11% of 620 MeV between 1 and 10 GeV)
Cherenkov “loss” : ECh
Proportional to 1/β2;
For 1 GeV: β = 0.995
For 2 GeV: β =  Nearly constant as a function of the energy
SP; Apr. 8, 2007
GDR Nucleon

17. Estimate the number of photons
Very crude estimation…(uncertainties…)
Muon ionization loss (4 GeV)
Efficiency ( µm): ~10%
Detected by PM: ~1300 g/GeV
For 283 MeV: ~370 photons
Muon Cherenkov “loss”
Number of Cherenkov g’s ( µm): ~200/cm;  9000 for 45 cm
Efficiency: ~10%
Detected by PM: ~900 photons
900/370 ≈ 2.4
Autiero et al., NIM A387 ( 1997) 352
More precise estimation needed: Monte Carlo being developed (Mainz U.)
SP; Apr. 8, 2007
GDR Nucleon

18. GAMS: e and µ peaks, 5 GeV GAMS: Cherenkov calorimeter ~625 MeV
SP; Apr. 8, 2007
GDR Nucleon

19. Shashlik: e and µ peaks, 4 GeV
Shashlik: Pb/scintillator sampling calorimeter
~280 MeV
SP; Apr. 8, 2007
GDR Nucleon

20. Shashlik calorimeter Homogeneous calorimeters: Sampling calorimeters
Ex: PbO, BGO, PbWO4, NaI, PbF2, …
Light is generated in the detector volume
PbO is radiation NOT tolerant
Sampling calorimeters
Ex: Pb/Scint, U/Ar U/Scint, etc…
Absorber and detector materials are separated
Radiation resistant
Delicate to calibrate
COMPASS decision
2008 hadron beam: replace the central part of ECAL2 with Shashlik (800 blocks) of Pb/scintillator
SP; Apr. 8, 2007
GDR Nucleon

21. Shashlik module Pb/scintillator sampling calorimeter
155 layers, 370x40x40 mm3
SP; Apr. 8, 2007
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22. GAMS calibration: 1 and 6 GeV
From: G. Khaustov
SP; Apr. 8, 2007
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23. GAMS: linearity and resolution (preliminary)
Analysis: G. Khaustov
SP; Apr. 8, 2007
GDR Nucleon

24. Shashlik: linearity and resolution (preliminary)
Analysis: G. Khaustov
SP; Apr. 8, 2007
GDR Nucleon

25. keeping the calibration constant
Monitoring or,
keeping the calibration constant
SP; Apr. 8, 2007
GDR Nucleon

26. ECAL2: calibration values
SP; Apr. 8, 2007
GDR Nucleon

27. ECAL1: LED amplitudes Variations not well understood SP; Apr. 8, 2007
GDR Nucleon

28. Laser monitoring, based on CMS design
Before the run:
Systematic hardware check
Measurement of the linearity block by block
Relative inter-calibration of all modules
During the run:
Performs individual channel hardware check online (LG transparency, HV, PM, electronics, SADC,… = all OK? )
Monitors short term and long term variations
Detects system self-failures
PbO cell
SP; Apr. 8, 2007
GDR Nucleon

29. Light distribution
SP; Apr. 8, 2007
GDR Nucleon

30. Test fiber bundle
SP; Apr. 8, 2007
GDR Nucleon

31. Fiber optical transmission – expected results
Optical transmission test bench
Relative transmission for 2151 fibers
SP; Apr. 8, 2007
GDR Nucleon

32. DVCS - the ECAL0 calorimeter
SP; Apr. 8, 2007
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33. Additional equipment to the COMPASS setupμ’
DVCS: μ p  μ’ p’ 
 ECal1 + ECal2
  10°
2.5m liquid H2 target
to be designed and built
+ additional calorimeter
ECal0 at larger angle
(° background)
L = cm-2 s-1
4m long Recoil Detector
to insure exclusivity
to be designed and built
Nμ=2.108/SPS cycle
(duration 4.8s,
each 16.8s) μ p’
SP; Apr. 8, 2007
GDR Nucleon

34. Calorimeter acceptances (Simulation DVCS)
xbj Q2
Existing Calorimeters
Xbj-bins
+ 4m x 4m ECAL0
SP; Apr. 8, 2007
GDR Nucleon

35. Photons in ECALs (Simulation from A.Sandasz)
<θγ> = 200 mrad
<θγ> = 72 mrad
<θγ> = 18 mrad
θγ [rad.]
θγ [rad.]
θγ [rad.]
<Eγ> = 7.6 GeV
<Eγ> = 19 GeV
<Eγ> = 54 GeV
Eγ [GeV]
Eγ [GeV]
Eγ [GeV]
SP; Apr. 8, 2007
GDR Nucleon

36. ECAL0 Dubna prototype - design
Lead/Scintillator type
200 mm long, 73x73 mm2
4mm Scint 4mm Pb
First tests at COMPASS end 2007
R/O: AMPDs
SP; Apr. 8, 2007
GDR Nucleon

37. Merci!
SP; Apr. 8, 2007
GDR Nucleon