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Status of MC Simulation at BESIII Collaboration Meeting

This document provides an overview of the status, performance, and planned developments of the MC simulation project at BESIII. It covers topics such as the BOOST framework, GEANT4 simulation, detector digitization, and physics interactions.

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Status of MC Simulation at BESIII Collaboration Meeting

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  1. Status of MC SimulationHuaimin LiuBESIII Collaboration meetingIHEP, Beijing, Jan. 12, 2006

  2. What to cover? • Retrospect • Current status • Performance • Planned development

  3. MC Project: BOOST on GEANT4 BESIII Object Oriented Simulation Tool (proposal: August, 2002) BES MC Software Evolution BESI BESII BESIII SOBER SIMBES BOOST EGS GEANT3 GEANT4 1980s 1990s 2000s

  4. Working group • IHEP Deng Ziyan (TOF, framework) He Miao (EMC) Liu Huaimin (framework, project coordinator) Yuan Ye (MDC) • PKU Mao Yajun (MUC) You Zhengyun (MUC, XML)

  5. BOOST architecture Event GENBES Generator Geometry Geant4 Tracking Detector Digitization Response Raw data MC truth HepEvt format Hit objects

  6. BOOST: 3 phases Phase 1: Framework prototype, simple geometry with hit Finished in May 2003 Phase 2: Detailed Geometry with simple digitization Finished in May 2004, MC data were produced to tune the reconstruction program Phase 3: Detailed digitization, physics validation Need information from beam test and data. We are here!

  7. BOOST working in BOSS Generator Simulation Generator Simulation Calibration Reconstructin Anaysis BOOST based on GEANT4 MC data BOSS based on GAUDI

  8. Status • Event generator All BESII event generators work in BESIII • MC-truth data (similar to MCMADE in BESII) Add more information for each sub-detector Useful for comparison between reconstruction and MC also for track-match extrapolation Still in Ascii format, binary format needed

  9. Status • Detector Description (new hardwire design) MDC: new MDC geometry with larger-angle axial layers TOF: new barrel TOF with double layer structure EMC: both barrel and end-cap EMC with support structure MUC: geometry with new alignment data (MDC axial cells and EMC irregular crystals) Insensitive regions: Beam-pipe super-conducting magnet

  10. Status • GDML (XML) Two options for detector description 1. Build the detector by Gean4 classes 2. Use XML file with GDML can be shared by reconstruction and event display Geometry Data file GEANT4 classes Detector G4 objects Simulation GDML converter Geometry XML file Reconstruction Event display ROOT converter Detector Root objects

  11. Status • Digitization MDC: wire resolution from beam test (two-Gaussian forms) other effects like Q-t correction, etc work with calibration group TOF: revisited, all physics mechanism considered EMC: photon statistics, noise, and electronic readout MUC: noise added

  12. Status • Magnetic field Still 1Tesla uniform field used inside the magnet Geant4 parameters (step size, intersection) optimized sensitive to momentum resolution 3-D simulated field map in the whole detector will come • Physics interactions 2 EM packages: standard (1 KeV) and low (100eV) Almost the same for BESIII Geant4 recommended hadronic packages (QGSP, …) Problem: some have strange behavior

  13. Performance • Running status Installed on different IHEP linux-platforms lxplus, besfarm, koala Running stable for about 1M physics events no crash, no dead-loop Easy to use in BOOST and BOOS user control card

  14. Performance • Simulation speed Depends on event type, cuts, machine, … Using Tester, Bhabha, Dimuon, Hadronic, inclusive J/Psi events CPU time, roughly, 1 second for one event on besfarm (PIII-933) Still slow compared with SIMBES Geant4 is 2 times slower than Geant3

  15. Performance • Memory consumption Roughly 80MB memory needed About 4MB memory leak for 10K events Memory leak depends on particle type, mainly comes from G4 interaction packages G4 is still in improvement

  16. Performance • Physics quantities Key physics quantities/parameters checked momentum/time/energy resolutions, reconstruction efficiencies, … They are close to the Design Report! (For detail, see other talks in this meeting) A good starting point for physics study

  17. Performance Sub-detector Designed MC MDC σw =130 μm 110 (beam test) σp/p = 0.5% 0.4% σdE/dx = 6-7% 6% TOF σt = 90 ps 85 EMC σE/E =2.5% 2.2% σxy < 6mm 4.8 MUC ε(μID) =95% 96% ε(π->μ)= 6% 6.2%

  18. MDC tracking performance μ- at pt = 1GeV/c Momentum resolution σ = 0.4MeV Momentum resolution Vs Pt (e-,μ-,π,p) Note: Fitted with single Gaussian in each bin.

  19. Effective speed Veff = 17.7 cm/ns Intrinsic time resolution at z=0 : 85 ps beam test result Effective attenuation length λ= 318cm

  20. EMC (barrel) Energy Resolutionsingle gamma

  21. Planned development • Move to new G4 and GDML – 02/2006 Gean4.7.1  Geant4.8.0 (12/2005) GDML1.0  GDML2.3.0 (08/2005) • Interaction packages – 12/2005 Study more hadronic packages Important but not urgent

  22. Planned development • Background simulation – 04/2006 BESIII background much higher than BESII Event mixing with beam related background Bian Jianguo is working on it • Trigger simulation – 12/2006 Implement trigger algorithm in offiline Cao Guofu is working on it

  23. Planned development • Real detector simulation – 12/2006? Detector performance changes with running time Rethink about BESII scheme BESII: a separate procedure for realization Using Calibration constants? Wire resolution/ efficiency, dead/hot channels, … • Detector response – 01/2006… Long-term work, work with calibration group

  24. Summary • Large MC data samples can be produced for physics study • MC performance is generally satisfactory • Physics validation in progress

  25. Thank you!

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