1. Status of MC Simulation Huaimin Liu BESIII Collaboration meeting IHEP, 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. Geometry Geant4 Tracking Detector Digitization Response Hit objects Event GENBES Generator HepEvt format Raw data MC truth BOOST architecture

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

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 Detector G4 objects Geometry XML file GEANT4 classes Simulation Geometry Data file GDML converter Detector Root objects ROOT converter Reconstruction Event display

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 σ w =130 μm 110 (beam test) σ p /p = 0.5% 0.4% σ dE/dx = 6-7% 6% TOF σ t = 90 ps 85 EMC σ E /E =2.5% 2.2% σ xy < 6mm 4.8 MUC ε(μ ID ) =95% 96% ε(π->μ)= 6% 6.2%

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

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

20. EMC (barrel) Energy Resolution single 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!