CBM Calorimeter system

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CBM Calorimeter system
I.Korolko (ITEP, Moscow)
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Outline
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SR Occupancy (24 K channels)
Occupancies are VERY high ! 1. SR thresholds
50, 60, 80 MeV 2. 10 MeV thresholds 40-50
occ. Do we need very high energy resolution ?
1. HEP experience NO 2. ALICE example YES
And it is much more interesting to build such a
good calorimeter Usual shashlik technology
exists already
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SR e-p separation
1. Compare track momentum with CALO energy
Use 2x2 matrix to minimize pile-up from
neighbors Most simple approach improvements
possible
2. Shower shape (2x2 / 3x3 ratio)
Gives additional factor 2 Rather simple approach
improvements possible
3. Preshower
Gives additional factor 2-3 (with 95 electron
efficiency) For rough sampling ECAL could
perform better
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SR Preshower
SR cut 2 MIPs
obviously could be increased with some loss of
electron eff.
SR width - 1.5 X0
Very fine ECAL sampling limits the possible width
of Preshower absorber
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SR e-p separation results
Depends on local occupancy Averaging over all
ECAL regions less than 5 GeV/c 50
5-10 GeV/c 200 greater than
10 GeV/c gt300
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Simulations
1. Standalone program working with 109 volumes
used for SR simulations will be used in the
nearest future (3-4-5 months) very fast 2minutes
/ central event with low GEANT thresholds
2. Migration to cbmroot
geometry and hit production Yuri Kharlov SR
algorithms nearest month
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Small exercises
Repeat SR simulations with rough sampling
almost the same results for e-pi separation
Repeat SR simulations with less CALO cells
worse results for e-pi separation (still in
progress)
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smaller Calorimeter
1. Reduce CALO acceptance

• Outer acceptance
• Inner acceptance

2. Make it rougher (number of plates)
3. Look for cheap photo-detectors (lower gain)
4. Reduce number of channels

• lateral granularity
• longitudinal granularity (Preshower)

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Outer acceptance

• electrons from J/? decays
• Pt gt 1 GeV/c
• Strong dependence -
• Small number of cells -
• Mostly high Pt particles -
• Worse e-pi separation
• Saving material, not money

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Inner acceptance