Pedro Arce (CERN/CIEMAT) (on behalf of CMS collaboration) GEANT4 CMS SIMULATION Pedro Arce (CERN/CIEMAT) (on behalf of CMS collaboration) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT) Outline OSCAR functionality OSCAR/GEANT4 robustness and performance Physics comparisons GEANT4 workshop 02 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 Building of XML geometry into GEANT4 ready Already can be visualised with IGUANA (heavily used for debugging) Missing: detector numbering schemes with new geometry Will need to review the use of ‘SetSmartLess’ (3 years old) Detailed checking quite advanced Thorough comparison of GEANT3 and GEANT4 geometry All materials, volumes and touchables properties Positions of touchable centres Material budget CMS Overlap Detection Tool (now in GEANT4) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT) Geometry for OSCAR 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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

OSCAR functionality: Primary generator CMS particle gun: Scan in , , energy Random (flat/gaussian) in , , energy Interface with HEPEVT ASCII files Interface with PYTHIA ntuples Long-life particles: In GEANT3 only the decay products are simulated In GEANT4 the particle is simulated before decaying (and the decay products are kept) Advantage: you take into account the possibility of interactions, energy loss, magnetic field bending, etc. before decaying The life time is not kept The momentum of decay products is not kept OSCAR: user can select to simulate the particles before decaying or simulate decay products (keeping the life time) Need deeper study to understand what will be the final solution GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

OSCAR functionality: Persistency Hits for all detectors Primary generator particles Selected tracks Use CMS framework (COBRA) Fully compatible with Reconstruction Using Objectivity, moving to ROOT (end 2002) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

OSCAR functionality: Visualisation Interactive visualisation is done with IGUANA Visualise any GEANT4 Geometry Select by logical volumes / by physical volumes Picking, slices Volume property window 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 Integrated with overlap detection Find overlaps, show result details in a list Highlight overlaps in 3D Hits, in the near future GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

OSCAR - IGUANA: magnetic field 2D plane that can be rotated Field direction as an arrow Field intensity as colour GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 end 2005) OSCAR milestone Spring/Summer 2003: “Reproduce the physics results of the GEANT3 simulation with similar performance” Physics Cuts: Production cuts per material Minimum kinetic energy cuts per material Still under investigation if we really need them Time of flight cut GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 (see wednesday talk by M. Stavrianakou) Documentation: User’s Guide updated for each release doxygen documentation Several Tutorials on the web For OSCAR developers For Physics Reconstruction software developers For Summer Students GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

OSCAR is ready for physics validation studies 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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 NOTE: new G4Exception found with GEANT4.4.1 (under investigation) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

GEANT4 vs GEANT3 Time Performance - Full events: H / tte / Z - Cuts in primary particles: Pt : 1 GeV, || < 2.4 (3.0) - Full CMS geometry - 3D TOSCA magnetic field - Production and tracking cuts as in CMSIM (GEANT3) - GEANT4 voxel navigation - GEANT4.4.0.ref02 - Pentium III 850 Mhz - Checked that they are really the same events (see next) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT) G3-G4 events detailed comparison H in all CMS (10 Events) Initial track energy No Tracks MeV Track length No Tracks mm GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT) G3-G4 events: detailed comparison Origin of secondary tracks: R vs Z R (mm) CMSIM (442828 tracks) Z (mm) R (mm) OSCAR (427136 tracks) Z (mm) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT) Time performance - H (10 events) CMSIM: 439k tracks 64 sec/evt OSCAR: 400k tracks 117 sec/evt (1.83) - tte (10 events) CMSIM: 1809k tracks 184 sec/evt OSCAR: 1159k tracks 425 sec/evt (2.31) - Z (10 events) CMSIM: 1105k tracks 96 sec/evt OSCAR: 941k tracks 248 sec/evt (2.58) GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMSIM(GEANT3) - OSCAR(GEANT4) comparison Central Tracker Number of rechits per track vs eta Cmsim 122 OSCAR 1 3 2 pre 03 RecHits 100 GeV Pt muons in region ||<2.5 resolution vs eta GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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

Importance of tuning tracking precision parameters Big difference between reconstructed and generated track parameters was found because tracking precision parameters were too high. ‘deltaIntersectionAccuracy’ is by default 100 m CMS tracker precision 20 m CMS Muon prcision 200 m Has to be set to 0.1 m Time just increased by 3% GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMSIM(GEANT3) - OSCAR(GEANT4) comparison: 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 GEANT4.4.0.p02 GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMSIM(GEANT3) - OSCAR(GEANT4) comparison: EM calorimeter Shower containment: From GEANT4 gallery: Electron 5 Gev in PbWO4 (more detailed) GEANT3 looks wider than GEANT4 From old test beam GEANT3/GEANT4 comparison CMS Note 1997/037 by A.Givernaud: good agreement with G3 for shower profile CMS Note 1998/031 by K.Lassila-Perini: G3 shower is a bit wider than real shower GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

CMSIM(GEANT3) - OSCAR(GEANT4) comparison: EM calorimeter Hit timing: GEANT4 shower has ~8% less hits than GEANT3 shower It doesn´t contradict with GEANT4 gallery plot below, however direct comparison is needed: GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison 1996 Testbeam Setup for CMS HCAL A test module of copper absorber plates with scintillator tile sampling 28 scintillator plates with absorber of varying thickness in between 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 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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison GEANT4 4.0.p02 100 GeV pi+ 0 Tesla ECAL+HCAL GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison 100 GeV e- 0 Tesla HCAL GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison pi+ 0 Tesla ECAL+HCAL Events with MIP in ECAL Events with shower in ECAL GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

ECAL + HCAL testbeam: GEANT3 - GEANT4 comparison pi+ 0 Tesla ECAL+HCAL Events with MIP in ECAL Events with shower in ECAL GEANT4 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)

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 comparisons 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 workshop 02 CMS GEANT4 Simulation Pedro Arce (CERN/CIEMAT)