1. Pedro Arce (CERN/CIEMAT)
GEANT4 CMS SIMULATION
Pedro Arce
(CERN/CIEMAT)
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

2. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
Outline
OSCAR functionality
OSCAR/GEANT4 robustness and performance
Physics comparisons
CMS - GEANT4 interaction 2002
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

3. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
OSCAR functionality
Geometry:
All CMS detectors
Also several testbeams
Currently moving to geometry in XML database, common to Simulation/Reconstruction/Visualisation
All geometry converted from GEANT3 geometry
Detailed checking in progress
Thorough comparison of GEANT3 and GEANT4 geometry done
All materials, volumes and touchables properties
Positions of touchable centres
Material budget
CMS Overlap Detection Tool (now in GEANT4)
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

4. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
Geometry for OSCAR
Future way: automatically building GEANT4 geometry from XML files
XML based Detector
Description Language
(XML DDL)
- Single description inter-
face for the ideal detector
- Generic description
. Materials
. Geometry
. Component approach
- Attaching specific
Information to
. Components
. Subsets of Volumes
- Human editable/readable
/expandable
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

5. View of 180 Higgs event simulated in CMS Tracker detector
Sliced view of CMS barrel detectors
View of CMS muon system
View of 180 Higgs event simulated in CMS Tracker detector
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

6. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
OSCAR functionality
Primary generator:
CMS particle gun:
Scan in , , energy
Random in , , energy
Interface with HEPEVT ASCII files
Interface with PYTHIA ntuples
Long-life particles: select to simulate then before decaying or simulate decay products
Persistency:
Hits
Primary generator particles
Selected tracks
Use CMS framework (COBRA)
Using Objectivity, moving to ROOT
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

7. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
OSCAR functionality
Interactive visualisation is done with IGUANA
Visualise any GEANT4 Geometry
Select by logical volumes / by individual copies / by category
Picking, slices
GEANT4 command line
A wizard to guide through OSCAR settings
Adding other extensions is trivial (e.g. GUIs like overlap detection)
Visualise Tracks
Visualise magnetic field
2D plane that can be rotated
Field direction as an arrow
Field intensity as colour
Integrated with overlap detection
Hits, in the near future
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

8. Example extension (a trivial wizard) IGUANA viewer displaying
OSCAR - IGUANA
Overlap detection
Example extension (a trivial wizard)
Queried from plug-in database, loaded on request and bound to IGUANA G4 Run Manager
Control of arbitrary
GEANT4 tree
Correlated
Picking
IGUANA viewer displaying
OpenInventor scene
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

9. OSCAR functionality Physics:
Electromagnetic processes needed at LHC
Hadronic processes needed at LHC
CMS Physics Technical Design Report is planned to be written using OSCAR (due 2005)
OSCAR milestone Summer 2003:
“Reproduce the physics results of the GEANT3 simulation with the same performance”
Physics Cuts:
Production cuts per material
Minimum kinetic energy cuts per material
Still to be investigated if we really need them
Time of flight cut
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

10. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
OSCAR functionality
UserActions:
Several user actions of the same type loadable on demand
Framework:
COBRA manages the main() and takes care of persistency
Now OSCAR is being reengineered to achieve full integration with CMS Framework
Documentation:
User’s Guide updated for each release
Several Tutorials on the web
For OSCAR developers
For Physics Reconstruction software developers
For Summer Students
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

11. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
OSCAR functionality
Future developments:
GEANT4e as GEANE replacement (error propagation for track fitting)
Under progress
GFLASH for fast simulation
RTAG/G4 discussion
Summary: OSCAR is ready for physics validation studies
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

12. OSCAR/GEANT4 robustness
Several problems found:
Particles loop between two volumes
 push them by 0.01 mm
Several G4Exception found:
solved by CMS team or/and with the help of GEANT4 team
 >10000 pp events without crashing
New G4Exception found recently in geant4.4.1.p01:
currently under investigation with the help of GEANT4 (see progress by delta review....)
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

13. GEANT4 vs GEANT3 Time Performance
- Full events in full CMS: H / tte / Z
- All CMS geometry
- 3D TOSCA magnetic field
- Production and tracking cuts as in CMSIM (GEANT3)
- geant4.4.0.ref02
- Pentium III 850 Mhz, 640 Mb
CMSIM(GEANT3) OSCAR(GEANT4) G4/G3
- H (10 events) seconds seconds
- tte (10 events) seconds seconds
- Z (10 events) seconds seconds
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

14. CMSIM(GEANT3) - OSCAR(GEANT4) comparison Central Tracker
Number of rechits per track vs eta
Cmsim 122
OSCAR pre 03
RecHits
100 GeV Pt muons in region ||<2.5
resolution vs eta
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

15. CMSIM(GEANT3) - OSCAR(GEANT4) comparison: Muon System
reconstructed – generator quantities
5-200 GeV Pt muons in region ||<2.4
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

16. CMSIM(GEANT3) - OSCAR(GEANT4) comparison: EM calorimeter
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

17. CMSIM(GEANT3) - OSCAR(GEANT4) comparison: EM calorimeter
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

18. CMSIM(GEANT3) - OSCAR(GEANT4) comparison: EM calorimeter
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

19. ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison
1996 Testbeam Setup for CMS HCAL
A test module of copper absorber plates with scintillator tile sampling exposed to pions, electrons and muons
28 scintillator plates with absorber of varying thickness in between
A prototype lead tungstate crystal electromagnetic calorimeter
Direction of magnetic field was parallel to the face of the scintillator plates (cms HCAL Barrel configuration)
Energies: 225 GeV muons (for calibration), 10 to 300 GeV pions, 10 to 300 GeV electrons
Magnetic Field: 0, 0.75, 1.5, 3 tesla
Configuration: Only HCAL or ECAL + HCAL
5000 events were taken for each setup
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 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

20. ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison
GEANT4 4.0.p02
100 GeV pi Tesla ECAL+HCAL
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

21. ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison
100 GeV e Tesla HCAL
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

22. ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison
pi Tesla ECAL+HCAL
Events with MIP in ECAL
Events with shower in ECAL
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

23. ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison
pi Tesla ECAL+HCAL
Events with MIP in ECAL
Events with shower in ECAL
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

24. CMS - GEANT4 interaction 2002
CMS requirements as presented in GEANT4 TSB meeting of 6/2/02
Problems with stuck particles/G4Exceptions:
Quite good answer from GEANT4 teams.
Most problems resolved
Implementation of reflections
Done end 2001
Some bugs found, solved after several months
Long lived particles: setting decay time
Already in GEANT4: communication problem
Cuts per material/volume
Cuts per material done by CMS  released in GEANT4 as a fast temporary solution
More diagnostic/debug tools, e.g. for Geometry checks. Others?
CMS Overlap Detection Tool included in GEANT4 release as an example in June release
GEANT4 tracking optimization in parameterized volumes
Done for June release
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

25. CMS - GEANT4 interaction 2002
Hadronic Model Issues (Testing-Review Documentation / information flow / Starting defaults for LHC experiments / Fluka?)
Documentation updated with GEANT4 releases
Consistent and explained physics lists provided
Response quite satisfactory
Updated documentation
Physics Reference Manual and User´s Guide for Application Developers updated
User´s Guide for Toolkit Developers under deep revision
Fast simulation program (e.g. GFLASH in GEANT4)
Under discussion by GEANT4 and RTAG
SWIG/Python interface
Under study
GEANE equivalent in GEANT4: error propagation for track fitting
Under progress by CMS team
Many ‘smaller’ bugs reported & removed
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

26. CMS - GEANT4 interaction 2002
New requirements
Parameterization of reflected volumes
Measure and improve time performance
Problems with stuck particles/G4Exceptions
Improve advanced documentation
GEANT4e requirements
Write own G4Navigator
Make public G4TrackingManager
Allow particles increasing energy
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

27. CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)
Summary
OSCAR is technically complete to start with physics studies
Some comparisons vs CMS GEANT3 simulation started
Some problems found, but solved by CMS + GEANT4
Some TestBeam comparison started:
Show reasonable agreement with data
Slightly better than GEANT3
Others to be done: ECAL TB ‘99, ECAL TB ‘02, ECAL+HCALTB ‘99, HCAL ‘02, Tracker ´02
Next months: systematic comparison with GEANT3 simulation
Plan to move to GEANT4 simulation by Summer 2003
GEANT4 response to CMS requirements and problems has been in general satisfactory
GEANT4 delta review 02
CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)