Status of BESIII Event Reconstruction System Zepu Mao IHEP BESIII Col. Meeting 2006/01/12

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

The T EST 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. T EST should be calculated by offline system. The Status of T EST (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.

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

By TOF T est : ns σ: 0.30ns T est : ns σ: 0.33ns T est : ns σ: 0.29ns preliminary result of T est performance “hadrons”, 10000, set T est to ”2”,”10”,”18” by MDC T est : 2.6ns, σ: 1.4ns) T est : 10.9ns, σ: 1.3ns) T est : 18.7ns, σ: 1.1ns)

MDC Tracking Module(1) (based on Belle Lib. Developed by S.L. Zeng )  Init: Geometry-Surv., Cal.-Constant, Adjust-constant Get Hit Information ….  R-  Tracking: Segment finding by conformal transformation and histogram method  Z Finding  3D Helix Fit Circle & Line Fit 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

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.

S-Z calculation in Z finding

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

Results from e, , proton, J/    , J/  e  e  1GeV; cos( θ ): -0.8~0.8. M0 (MeV) Eff (%) dr ( μ m) dz (mm) σ xy ( μ m) σ P (MeV) Chi2nHits EE  Proton J/     J/  e  e 

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 δ p /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 …..

MDC SegFinder Sequence For every superlayer and every wire in 2 nd layer form a group of 8 wires Try 4 hit pattern for this group Call tryPatterns() Try 3 hit pattern for this group Call tryPatterns() Set massage of segment list Sequence of segFinder::createSegs() For every group 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.

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

Efficiency Vs Pt (e,μ,π,p) Average efficiency >98 % z 0   0.8 mm d 0   0.1 mm Nhits used in tracks comparison with MC truth

 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. Status of dE/dx Module (Developed by D.Y. Wang)  6%

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

dE/dx seperation for 5 particles(MC) seperation power with dE/dx Pre. Performance of dE/dx(2) 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

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.

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, LAttenuation  3.2m, Time Res.  62 ps

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

The Status of EMC Rec. ( developed by Wang Zhe and He Miao ) Digit HitCluster Shower Emc Digit Emc Mc Hit from TDS Input : Emc Rec Shower to TDS or Root Output: Data Flow The Code EmcRec has finished the design, programming for barrel and end-cap and work well in V5.0. Performance: Eff:  100%  E  2 % for gamma with 1 GeV e /π separation studied    5mm,    5mm in barrel  E  2.5%,    6mm,    6mm for endcap

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

Pre. Performance of EMC Endcap 1GeV gamma west endeast end σ E /E vs layer  Res. (cm) vs layer  Res. (cm) vs layer  E  2.5%,    6mm,    6mm

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” : cos θ (-0.9~0.9) Eff=98.9% for 1.GeV Eff=93.3% for 0.5GeV

Muon ID Efficiency GeV/c % Mu Efficiency Pi Fake rate Mu Efficiency Pi Fake rate 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;

 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 Output parameters from KalFitAlg proton events 1GeV/c  Package is migrated and work on V5, 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 )

Summary(1) Module Name Pre. Results by general checking 1 MDC Fast track Trk-Eff  99 %,  x  160um,  z  4mm,  p  10MeV 2 EvTime 95% events got exact T EST, err less 1% 3 MDC-Track-1 Trk-Eff  99%,  p  6 MeV,  x  140  m,  z0  2 mm 4 MDC-Track-2 Trk-Eff  99%,  p  4 MeV,  x  110  m,  z0  0.8 mm 5 dE/dx PID  6%, π/K 3  seperation about 800MeV/c 6 Trk-Ext Work well on V5 7 Klmfit Work well on V5 8 TOF Rec. LA Trk-Eff  98 %,  T  62ps, LA  3.2m 9 EMC Rec. Trk-Eff  100 %,  E  2%, special resolution about 5mm 10 MuC Rec. Trk-Eff  %

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.

谢谢 Thanks

T est Calculation by TOF A B TOF PMT Z=0Z TOF Charged particle scintillator D C A->B: By MDC fast tracking B->C: By information of TOF & fast track constants  T est = TDCM(tof) － t ev

C->D by MDC information Sense wire Field wire Drift cell A (t est ) B C D T est Calculation by MDC B->C by MDC track & Information A->B by MDC fast track constants  T est = TDCM(MDC) － t ev

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

BEPCII Milestones May. 04 – Oct. 04. : –Linac upgrade –BESII detector removed Nov. 04 – March 05: SR running April 05 – Jan. 06: Long shutdown –Remove existing ring –Install two rings –Cryogenics system ready for SC devices, field mapping Feb.- Sep. 06: Tuning of machine + SR running Oct. 06 : BESIII detector moved into beam line Nov. 06 – Feb. 07 : Machine-detector tuning. Physics run by March 2007

BES III 离线软件系统研发时间线

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