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Status of BESIII Event Reconstruction System Zepu Mao IHEP 100049

Status of BESIII Event Reconstruction System Zepu Mao IHEP 100049. BESIII Col. Meeting 2006/01 /12. The events Reconstruction system. 1 MDC Fast track. MDC Tracking. 2 Event Start Time. 3 MDC-Tracking-1.

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Status of BESIII Event Reconstruction System Zepu Mao IHEP 100049

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  1. Status of BESIII Event Reconstruction SystemZepu Mao IHEP100049 BESIII Col. Meeting 2006/01/12

  2. The events Reconstruction system 1 MDC Fast track MDC Tracking 2 Event Start Time 3 MDC-Tracking-1 4 MDC-Tracking-2 5 Kalman fit 6 Track Ext. 7 dE/dx PID EMC Rec. 8 TOF Rec. TOF Rec. 9 EMC Rec. MU Rec. 10 MuC Rec.

  3. The Status of TEST (Event Start Time) Module (1)developed by X. Ma • Finished the programming and testing by TOF and MDC-fast tracking and got Pre. results. • Continue to test the codes for cosmic events • continue to study the new method for MDC-fast tracking fail case. The TEST is important for the momentum Res., spatial Res. of the charged particles, but it is uncertain in the online system due to: 1) The BESIII trigger system can’t separate every event up to beam bunch. 2) The start time of charged event is determined by TOF_T, but the TOF reach time is different for different particle and different momentum. TEST should be calculated by offline system.

  4. Preliminary results of Code performance e-e+ ->hadrons, set TEST=0 by TOF(90.2%) * barrel 84.73% , * end-cap 5.47%) * Test: 0.01ns * σ: 0.27ns • 95%events got exact TEST • judgment error: 0.88% * 5% need Cal. by MDC new method • by MDC( 4.8%): • Test: 0.75ns • σ: 1.17ns

  5. preliminary result of Test performance “hadrons”, 10000, set Test to ”2”,”10”,”18” By TOF Test: 1.998 ns σ: 0.30ns Test: 10.01 ns σ: 0.33ns Test: 18.02 ns σ: 0.29ns by MDC Test: 2.6ns, σ: 1.4ns) Test: 10.9ns, σ: 1.3ns) Test: 18.7ns, σ: 1.1ns)

  6. MDC Tracking Module(1) (based on Belle Lib. Developed by S.L. Zeng ) • Finished the coding and Pre. Checking, the Pre. Results are reasonable • More works need to do: increasing the efficient for low momentum tracks & add noise case. • Increasing the multiple tracks separation ability • optimizing the parameters of the codes • Init:Geometry-Surv., Cal.-Constant, Adjust-constant Get Hit Information …. • R- Tracking:Segment finding by conformal transformation and histogram method Circle & Line Fit • Z Finding • 3D Helix Fit

  7. Segment Finding Algorithm • Conformal transformation. A circle which passes through the origin is transformed into a line. • Segments found by histogram of hit wires’ azimuthal angle • Track linking from the outmost to the innermost layer with the directions of segments and apply the circle fit.

  8. S-Z calculation in Z finding

  9. The Pre. Performance of MDC Tracking(1) σxy~ 139μm σP~5.7MeV/c σ(dr)~179μm σz ~1.9mm from 1 GeV - pt/pptvs momentum xyvs momentum Nhits vs momentum Eff vs momentum

  10. Results from e, , proton, J/, J/ee 1GeV; cos(θ): -0.8~0.8.

  11. MDC Tracking Module(2) (based on Babar Lib. Developed by Yao Zhang ) • Finished the lots of work of migration, Geometry changes, Stereo track finding algorithm improved, system conversion: (track parameters)…, • work well in V5 and used by physics study • The Pre. performance of the codes is: tracking efficiency > 98% , spatial resolution about 110 μm, momentum resolution δp/p = 0.4%. • Testing further with MDC calibration constants • Further checking to increase the efficiency in low momentum and add noise case. • optimizing for the parameters of the codes …..

  12. Sequence of segFinder::createSegs() 7 6 5 For every superlayer and every wire in 2nd layer form a group of 8 wires 4 3 2 For every group 1 0 Try 4 hit pattern for this group Call tryPatterns() Try 3 hit pattern for this group Call tryPatterns() 1 7 6 0 0 5 1 4 0 3 2 1 1 0 0 1 Set massage of segment list MDC SegFinder Sequence Wires No. 0-7  Set one word for a group of 8 wire, each bit for a wire.  Set “1” for a hit wire, others “0”  This octal value used for its group No.

  13. The Pre. Performance of Tracking Mode(2) e- at pt = 1GeV/c Momentum resolution p 0.40% e- at pt = 1GeV/c Spatial resolution xy 110μm

  14. Nhits used in tracks comparison with MC truth Efficiency Vs Pt (e,μ,π,p) Average efficiency >98 % d0  0.1 mm z0  0.8 mm

  15. Status of dE/dx Module(Developed by D.Y. Wang) • dE/dx codes developed successfully, released for physics study. • More reconstruction algorithms studied to get best performance • Particle ID is tested with MC samples, dE/dx resolution, distributions, PID efficiency is reasonable. 6%

  16. Pre. performance of dE/dx(1) χ distribution for Kaon sampleProb（K）distribution for Kaon sample • Distribution of is nearly a normal N(0,1)distribution • Distributions of probability function are flat

  17. Pre. Performance of dE/dx(2) dE/dx seperation for 5 particles(MC) seperation power with dE/dx • Good particle seperation in a wide range for different particles • The π/K seperation(3 σ ) reach about 800 MeV/c • Particle identification efficiency is more than 90% with MC samples

  18. Track Extrapolation Module(based on Belle Lib. developed by L. L Wang)  Function:Extrapolate MDC tracks to Outer detectors: TOF, EMC and MUC  Algorithm: based on GEANT4, Energy loss and Magnetic field. Multiple scattering effect put into error matrix.

  19. The Status of the TOF Rec. Module(based on Belle Lib. developed by Linli Jiang) • TOF Rec. package has been developed, and run well on V5 • The Pre. performance is: • The Efficiency is about 99.8% with 1 GeV single e LAttenuation  3.2m, Time Res.  62 ps

  20. Pre. Performance of TOF Rec. code Checked by “LUND” MC data sample Mass distribution Beta vs Momentum Mass distribution

  21. The Status of EMC Rec.(developed by Wang Zhe and He Miao) Data Flow • The Code EmcRec has finished the design, programming for barrel and • end-cap and work well in V5.0. • Performance: • Eff: 100% Shower Digit Hit Cluster E 2 % for gamma with 1 GeV 5mm,5mmin barrel E 2 .5%, 6mm, 6mmfor endcap Output: Input: Emc Digit Emc Mc Hit from TDS Emc Rec Shower to TDS or Root • e /π separation studied

  22. Pre. Performances of EMC Barrel 1GeV gamma Energy Resolution vs E By single gamma Position Resolution vs E theta E 2 % for gamma with 1 GeV 5mm Position Resolution vs E phi 5mm

  23. Pre. Performance of EMC Endcap 1GeV gamma E 2 .5%, 6mm, 6mm σE/E vs layer  Res. (cm) vs layer  Res. (cm) vs layer west end east end

  24. MUC Reconstruction Module(developed by Z.Y You) • Finished the programming and testing by “Extrapolating MDC Tracks”and “2D/3D Road” tracking method. • * The  ID method also studied. • “2D/3D Road” : Tracking EF:  99% • “Extrapolating” : cosθ(-0.9~0.9) Eff=98.9% for 1.GeV Eff=93.3% for 0.5GeV

  25. Muon ID Efficiency MuID Alg Global : MucRec + MuID For all tracks with |Cos θ| < 0.9 Mis-identified muon includes : 1. Lost hits by Acceptance; 2. Lost hits by muc reconstruction; 3. All hits found, but mis-identified as pion by MuonID Algorithm;

  26. Package is migrated and work onV5, Five particle hypotheses is made; the materials is updated with BESIII’s. Kalman filter track fitting package(based on BELLE Lib. Developed by D.Y. Wang ) • Helix parameters and error matrix looks reasonable. • 5 Parameters of a track is reasonable comparison with MDC-Tracking’s. (but not improvement too more.) • lots of work need to do, Parameters need further optimizing. Output Pull check Input Helix parameters from FastTrkAlg proton events 1GeV/c Output parameters from KalFitAlg

  27. Summary(1)

  28. Summary(2) • We finished lots of works: code design, programming, code • migration, code test, algorithm study, code optimization … • Almost all sub-system work well on the V5, got the Pre. • Performance by the simple data sample, and released for • physics study. • The results is different from two MDC Tracking codes, • due to the data sample is different. We will check the codes • and data(new MDC geometry) later. • More works need to do to make each code work in the best • status by closely the data to real data case step by step.

  29. 谢谢 Thanks

  30. Test Calculation by TOF Z=0 ZTOF Charged particle TOF scintillator D C PMT B B->C: By information of TOF & fast track constants A->B: By MDC fast tracking A • Test = TDCM(tof) － tev

  31. Test Calculation by MDC Sense wire C D B Field wire Drift cell B->C by MDC track & Information C->D by MDC information constants A->B by MDC fast track A (test) • Test = TDCM(MDC) － tev

  32. Fig.6 Flow of R-phi track finding(left) and z finding(right)

  33. Structure of TOF • Aim: particle identification (PID) Barrel TOF Endcap TOF

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