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CALORIMETERsystem for
the CBM detector
Ivan Korolko (ITEP Moscow)
CBM Collaboration meeting, October 2004
Outline R&D studies
technology development
prototype module
beam tests this summer
quality control of mass production
MC feasibility studies
Technology development
Physics on CBM:
1. low energies → energy resolution → fine sampling
very thin lead plates
2. high multiplicities → small Moliere radius
very thin plastic plates
HERA-B, LHCb : 2.0 mm lead, 4.0 mm plastic, 9%/sqrt(E)
RD36, IHEP : ~0.4 mm lead, 1.5 mm plastic, 3%/sqrt(E)
Future CBM : ~1mm lead and plastic plates, ~5%/sqrt(E)
Technology development (Vladimir)
Technology development (Vladimir)
Prototype module
Dimensions – 122 x 122 mm2 (9 light isolated cells)
280 lead plates - 0.5 mm thickness (25 X0)
9x280 plastic plates - 0.5 mm thickness
16 WLS fibers + 1clear fiber per cell
GEANT simulations predict ~3%/sqrt(E) resolution
(sampling fluctuations only !!!)
Prototype module
Prototype module
Beam tests
Measurements:
1. Energy scan with electrons 5-100 GeV/c
energy resolution
2. Scan with 100 GeV/c muons
light collection efficiency (!!!)
We need some time to analyze test beam data
Beam tests
Light yield:
800-900 photo electrons per GeV (after a lot of skepticism)
additional 3%/sqrt(E) term in energy resolution
LHCb modules : ~4500 photo electrons per GeV
factor 2 is lost due to the reduced volume ratio (Moliere)
factor 3 is lost due to the small thickness of plastic
(4 mm LHCb vs. 0.5 mm !!!)
Conclusions – 1mm plastic plates would be better
Production quality is important
Beam tests
Beam test results allow us:
1. To understand light collection efficiency for a wide range of different plastic plates (0.5 mm – 4.0 mm)
Special light transport MC code is developed and tuned with experimental data
2. To improve pure GEANT MC with 2 important features
a) light yield (as a function of plastic thickness)
b) light collection eff. (as a function of plastic thickness)
Production quality
Trigge
r
Trigge
r
Set-up designed for Set-up designed for 30 modules30 modules
Measuring 5 inner Measuring 5 inner modules at oncemodules at once
Using vertical tracksUsing vertical tracks
Exposure time ~20 hExposure time ~20 h
mixer
PM
mixer housing
1. Complex quality control system in Vladimir (plates+modules)
2. Cosmic muon setup at CERN to check all LHCb modules
Production quality
25 lines measured already
125 inner modules (1125 cells)
The overall width of MIP signal is about 12 %
(still to be improved)
Production quality
Signal seen by one PMT in 25 different cells.
More accurate estimation of module (cell) quality
Cells are the same within 6%
R&D conclusions
First prototype was built and tested
1. Very fine sampling (0.5 mm lead and plastic plates)
2. Adequate light output (even for 0.5 mm plastic plates !!!)
We are confident that required module could be built
uniformity of light collection efficiency is an issue
We have data for tuning of pure GEANT MC which is rather important for further feasibility studies
Quality of LHCb modules is very good…
MC feasibility studies
e/π separation
Overlap MinBias (central) events with electrons from J/ψ decays
Studying e/π separation (full CBM MC) as a function of:
1) electron production angle
2) calorimeter granularity
Simple but very CPU consuming exercise.
MC feasibility studies
μ/π separation
Overlap MinBias (central) events with muons from J/ψ decays
Studying μ/π separation as a function of:
1) electron production angle
2) calorimeter granularity
Requires longitudinal segmentation !
MC feasibility studies
Registration of neutral particles – γ, antineutrons
Interesting for many applications
Opens possibility to register strange barions with neutral particles in final state:
1. anti-(Σ-) anti-(n) + π+
2. Σ0 Λ + γ
3. exotics… (like antipentaquark)
Other suggestions are welcomed
MC development
Sergey Kiselev has prepared description of the calorimeter
for the last version of CBM MC – cbmroot.