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Validation of GEANT4 by the CMS Experiment. Pedro Arce (CIEMAT/CERN) On behalf of the CMS Simulation Group GEANT4 Workshop ’03, TRIUMF, 2nd August 2003. Index. Status of CMS GEANT4 simulation (OSCAR) Silicon tracker studies EM calorimeter studies Muon physics studies - PowerPoint PPT Presentation
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GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 1
Validation of GEANT4 by the CMS Experiment
Pedro Arce (CIEMAT/CERN)
On behalf of the CMS Simulation Group
GEANT4 Workshop ’03, TRIUMF, 2nd August 2003
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 2
Index
Status of CMS GEANT4 simulation (OSCAR)
Silicon tracker studies
EM calorimeter studies
Muon physics studies
Hadronic calorimeter studies
Conclusions
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 3
OSCAR status
OSCAR (Object Oriented Simulation for Cms Analysis and Object Oriented Simulation for Cms Analysis and Reconstruction)Reconstruction) is (almost) ready to substitute GEANT3-based simulation in the official CMS production
Extensive physics checking has been carried to test GEANT4 physics vs. GEANT3 and vs. TestBeam data where available
1.2 M single particle events + 300 k full events have been produced
CMS DC04 challenge (50 M events) have started this summer with GEANT3 simulation, we hope to make a major part of this production with GEANT4
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 4
OSCAR status (II)
CPU is acceptable: 1.5 - 2 X GEANT3
Memory is acceptable: 220 Mb OSCAR vs. 100 Mb GEANT3 simulation
Crashing rate is acceptable: 1 / 20000 events
Becoming smaller at each GEANT4 release
Still some problems in tracking and hadronic physics
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 5
View of CMS muon system
Sliced view of CMS barrel detectors
View of CMS pixel detector
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 6
dE/dx in Silicon Detector
• dE/dx has been studied for:– Particle Types: Muon, Pion, Kaon and Electron– Momenta: 2, 3, 4, 5 and 10 GeV
• It is compared with:– GEANT3– ALEPH data– PHOBOS data
OSCAR (GEANT4) CMSIM (GEANT3)
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 7
dE/dx in Silicon Detector (II)
RELATIVISTIC RISE
• We do not have that much data available ;)
– PHOBOS: relativistic rise for pions between 0.5 – 8 GeV is 4% (with pads!)
– ALEPH: relativistic rise for pions between 1 – 18 GeV is 7% (but only 2 layers!)
– We lack any data about electrons
– GEANT4/GEANT3 with the proposed settings: we “measure” a 4% rise between 1 and 10
GeV.
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 8
Resolutions in Silicon Detector
Pt resolution:
Lower resolution probably due to smaller spread from multiple scattering (~< 10 %)
PT = 10 GeV
PT = 100 GeV
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 9
EM calorimeter
• SETUP: • CMS electromagnetic calorimeter: lead tungstate crystals pointing to interaction point• Photon of E = 30 GeV enters front face of crystal• No magnetic field
• What was compared:• E in hottest crystal, in 3x3, in 5x5 matrix• E total
• dNhits/dt, for 1 ns time slices
• GEANT3.21 vs. GEANT4.5.1
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 10
EM calorimeter
Shower shape: From GEANT4 gallery:Electron 5 Gev in PbWO4
(more detailed)
• GEANT4 electromagnetic shower looks thinner than GEANT3• Test beam data seems to agree with GEANT4
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 11
Energy resolution in EM calorimeter
GEANT4
GEANT3
GEANT4
GEANT3
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 12
Muon Physics
Single block of iron
• To concentrate on physics differences• Similar results for other materials
Single muons of 10, 100, 1000 GeV • Energy loss• Delta rays• Bremsstrahlung• Pair production• Muon nuclear interaction (negligible)• Multiple scattering
Dependency with production cuts (plots shown with 0.1 mm)
Check new ´integral´ processes in GEANT4 (GEANT4.5.0.ref02)
– No difference found
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 13
Total Energy Lost
10 GeV
100 GeV
1000 GeV
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 14
Bremsstrahlung
10 GeV
100 GeV
1000 GeV
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 15
Pair Production
10 GeV
100 GeV
1000 GeV
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 16
Multiple scattering
10 GeV
100 GeV
1000 GeV
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 17
Multiple scattering
LEP I Z events in L3 detector (45 GeV)
50 GeV GEANT3.21 vs
GEANT4.5.2.ref01GEANT3 GEANT4.5.2.ref01
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 18
Muon Physics
PT Resolution:
GEANT3
GEANT4
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 19
EM calor. + Hadr. calor. testbeam
2002 Testbeam Set-up for CMS HCAL• A module of copper absorber plates with scintillator tile sampling
• 28 scintillator plates with absorber of varying thickness in between (only 3 samplings)
• A prototype lead tungstate crystal electromagnetic calorimeter• Energies: 225 GeV (for calibration), 10-300 GeV , 10-300 GeV e-• Magnetic Field: 0, 0.75, 1.5, 3 tesla (direction parallel to the face of the scintillator)• Configuration: Only HCAL or ECAL + HCAL
• 5000 events were taken for each set-up• Response of the Calorimeter was studied as a function of:
• Magnetic field: effect on scintillator• Absorber thickness: optimisation of resolution versus containment• Absorber depth: energy containment • Electromagnetic Calorimeter contribution: e/ effects
• GEANT4.4.1 (physics list 1.8)
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 20
Resolutions: M.C. & data agree very well
Source of discrepancy could be e/h (e.m. & nuclear x-sec), punch through (shower length) ?
Resolution and Energy Response
• All known contributions to ECal and HB resolutions added• Ecal resolution “matched” to data measured e- resolution
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 21
Hadr. calor. GEANT4 vs GEANT3
- 50 GeV: Energy deposited in each layer of Hadr. Calor. shows good agreement GEANT3-GEANT4
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 22
Hadr. calor. GEANT4 vs GEANT3
- 20, 30, 50, 100, 300 GeV: Energy deposited in EM Calor., Hadr. Calor. and outer layers of Hadr. Calor. is different
GEANT4 shower is shortero Test beam data seems to agree better with GEANT3, new data being analysed now
EM Calor. Hadr. Calor. Outer layers Hadr. Calor.
GEANT4 workshop ’03 GEANT4 Validation by CMS Pedro Arce(CIEMAT/CERN) 23
Summary
CMS GEANT4-based simulation is almost ready to substitute GEANT3 one
Big effort has been made during recent months to compare GEANT4 with GEANT3 and with Test Beam data where available
Small differences observed sometimes
Precision of test beam data can hardly favour GEANT3 or GEANT4 in most cases
All physics groups agree in switching to GEANT4 as official CMS simulation tool