1. The BESIII Offline Software Weidong Li Institute of High Energy Physics, Beijing Workshop on the cooperation of PRC-US in HEP 16 June 2006

2. 2 BESIII Experiment Muon Chamber (MUC) ： RPC based TOF System ：  T = 90 ps barrel 110 ps endcap Main Drift Chamber (MDC) ：  xy = 130  m  P/P = 0.5 %@1 GeV  dE/dx = 6-7 % EM Calorimeter (EMC) ：  E/E = 2.5 % @ 1 GeV  z,  = 0.6 cm @ 1 GeV Super-conducting Magnet ： 1.0 Tesla

3. 3 Software Environment  Underlying framework GAUDI (originally developed by LHCb)  Simulation GEANT4  Other external LIBs: CERNLIB, CLHEP, ROOT, AIDA, XercesC, GDML …  Database: MySQL  Computer language: C++ (BESII legacy code written in Fortran )  Operation system: SLC3/ gcc3.2.3  Reused part of code from Belle, BaBar, ATLAS,GLAST

4. 4 CMT and CVS Release area CVS Work area sources Installation area binaries package generated cmt package cmt External  Internal software  External software HEP software Public domain software

5. 5 Gaudi Infrastructure  The application has an ApplicationMgr and it creates and initializes a set of services.  The EventLoopMgr controls the main physics event loop and schedules execution of algorithms.  We have implemented many BESIII specific Algorithms and Services.

6. 6 Framework Geometry GDML DataExecution Sequence Sequence Raw Data RootDst CnvSvc RawData CnvSvc TofGeom Svc MdcRec TofRec MucRec DST Data Event Data Service EmcRec Detector Data Flow Flow Event Data Flow Flow Navigation Svc Magnetic FieldSvc PartProp Svc MdcGeom Svc EmcGeom Svc MucGeom Svc

7. 7 Event Data  HEPEVT Data Kinematics information only  RAW Data Delivered by DAQ for reconstruction Byte stream format  Simulated Event Data Contain digits, hits and other MC truth information Root format/byte stream format  REC & DST Data Reconstructed Data is event data written as output of reconstruction procedure DST Data is a reduced event representation suitable for analysis Both in ROOT format RAW Data Simulated Event Data Event Data Generator HEPEVT Data Data G4 Simulation Reconstruction REC & DST Data Data

8. 8 Simulation (1)  MDC  TOF Scintillator (EJ200) Wrapping materials (Al + PVF) PMT (R5924) Stereo layers: Hype Stereo Cells ： TwistTube Axial layers: Tube Solid Tube & Endplate constructed use Tube solid barrel end-cap

9. 9 Simulation (2)  EMC G4Trap & G4IrregBox Added cables,support system Digitization: readout electronics is simulated  MUC Detector description detailed to a single strip One dimension read-out Efficiency added according to position of pad

10. 10 Simulation (3)  Generators are legacy code from BES/BESII experiment  Generators communicate with detector simulation through Gaudi Transient Data Store. Generator (BesGenModule) Simulation (BesSim) Reconstruction (MdcPatRec...) Kine Inform. Digi & McTruth Event Gen McTruth Digi Recon Dst Algorithm Transient Data Store 1 2 3 4

11. 11 Reconstruction Algorithms Sub-detectorReconstruction Algorithms MDC MdcPatRec : tracking algorithm based on BaBar software TrkReco: tracking algorithm based on Belle software MdcDedxAlg: calculating dE/dx information for MDC tracks. KalFit: track fitting algorithm using the Kalman Filter method. TOF TofRec: calculates the flight time of charged particles. Calorimeter EmcRec: a clustering algorithm for EM Calorimeter. Muon Chamber MucRec: tracking algorithm for Muon Chamber Other Algorithms T0 Calculation: determining the event start time T0. Tack Extrapolation: considering particles’ deflection in the magnetic field and the ionization energy loss of particles in the material.

12. 12  Recon. and simulation algorithms retrieve calibration data from calibration data store  Meta-data stored in database contains: path, valid run interval  Calibration constants are stored in ROOT files Calibration constants (ROOT) MySQL database CalibFunc Svc Calibration Data Service Reconstruction algorithm CalibRoot CnvSvc Simulation algorithm GUI Client Calibration Algorithm

13. 13 Event Display Tool: BesVis  Based on ROOT, OpenGL, X3D and XML  Support both 2D and 3D view  Operations and controls available through menu and toolbar items  Recently MCTruth information was added.

14. 14 Physics Analysis Software  Analysis Object Builder  Particle Identification  Kinematics Fitting  Vertex Finding

15. 15 Major Releases  BESIII alpha release integration with BOOST simulation Running the reconstruction chain for MDC, TOF, EMC and MUC can be achieved in the BESIII Gaudi framework. EDM for both Raw Data and reconstructed data developed. Completion of fully functional Event Data I/O. Status: published in May, 2005  BESIII beta release Simulation and reconstruction chain functions reasonably well and can successfully process thousands of events. Common physics analysis tools and utilities available. Physics study can start. Status: published in November, 2005

16. 16 Event Data Flow

17. 17 Performance (1)  TOF reconstruction eff. ~99% (1GeV electron) time resolution: ~110 ps   MDC momentum and spatial resolution σxy = 110 μm, δpt/pt = 0.4% (1GeV μ)  dE/dx = ~6% 1 GeV π

18. 18 Performance (2)  MUC Recon. efficiency: ~ 99% @ 1GeV Ratio of fake μ < 10% for π   EMC σ E /E ≈ 2.8%@1GeV σ z = 0.6 cm @1GeV μ efficiency π (fake μ ) 90 70 50 40 30

19. 19 BESIII Software Timeline

20. 20 Ongoing Activities  Detector alignment survey  Mixing of background events  Reconstruction performance optimization  Studies of algorithms’ robustness With background pileup miss-alignment Non-uniform magnetic field  Data Challenges

21. 21 Summary  BESIII has successfully adopted GAUDI application framework.  Based on Gaudi, the BESIII offline software was developed Simulation Calibration and reconstruction Physics analysis  Data challenge and software performance optimization are the major task for 2006.