calorimeter system for the cbm detector ivan korolko (itep moscow) cbm collaboration meeting,...

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.