Status of BESIII Event Reconstruction System Zepu Mao IHEP 100049 BESIII Annual Meeting 2005/05/29.
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Transcript of Status of BESIII Event Reconstruction System Zepu Mao IHEP 100049 BESIII Annual Meeting 2005/05/29.
Status of BESIII Event Reconstruction System
Zepu Mao IHEP 100049
5
IHEP简介
BESIII Annual Meeting 2005/05/29
The Modules and General Flow
TOF
Rec
MuC
Rec.
Veefind Evtvert
Fast-
Track
Even
t-Tim
e
MD
C-
Track
Even
t-Tim
e
Track
-F
it
dE
/dx-R
ec
Trac-E
xt
MDC Tracking
Clu
ster M
atch Gam
ma
Pi
0EMC Rec
Phy. Vertex
MDC Fast Tracking Module
x160 m
z 6mm
p 10MeV
Trk Eff 99%
x160mz6mm
p10MeV
data unpacking
axial segments finding stereo segments finding
2D track finding
2D track fitting
3D track finding
S_Z track fitting
The begin point differences between the the bunch and trigger system :
0,8,16 ns
Bunch Interval: 8 ns
Trig. F: 25 ns RF/12=41.65MHz
RF 2 ns
Why need to do Event Time?
Event Time Module Status Due to the trigger system can’t separate the events from beam bunch, the time of Events starts point need calculate in offline system by the geometry of TOF and MDC.
MDC Tracks
MDC TOF Raw
Tof Infor.
EvTime-TOF EvTime-MDC
yes no
yes no EvTime-MDC0
• EvTime-MDC and EvTime-TOF:
passed the testing by MC data
using the information of MDC
fast tracks.
EvTime-MDC0: for “No MDC Fast tracks” events is studying
MDC Tracking Module(1) (based on Belle)
Init: Geometry-Surv., Cal.-Constant, Adjust-constant Get Hit Information ….
R- Tracking: Segment findingby conformal transformation and histogram method
Z Finding
3D Helix Fit
Circle &
Lin
e Fit
Status MDC Tracking Module (1)
z0 2 mm
x 140m
D0 180m
p 6MeVTRK Eff 99%
MDC Tracking Module(2) (based on Babar)
Init: Geometry-Sur., Cal.-Constant, Adjust-constant Get Hit Information ….
Link segments to 2-D tracks,
3D Helix Fit
Lin
e & C
ircle Fit
Tracking:
Segment finding:Search segments in each super-layer using a pattern look-up table.
Add stereo segments
Status MDC Tracking Module (2)
This module has been tested by MC data also.
The preliminary performance is:
pT 5.8 MeV
TRK Eff 95%
Kalman filter track fitting package(based on the (BELLE Lib.)
Simplicity and flexibility in computation :
more reliable material effects and NUBF treatments
Optimal predictions from both ends
Easy outlier and ambiguity removal
Good match to OO design & programming
• Recursive procedure to estimate track parameters
prediction
filtering
smoothering
Preliminary Results of Kalman Track fit
Helix parameters and error matrix is roughly reasonable. Parameters of track consistent with MdcFastTrkAlg’s. Parameters need further optimizing.
Output Pull check
Input Helix parameters from FastTrkAlg
Output parameters from KalFitAlg
proton events 1GeV/c
Package is migrated successfully on the BOSS V4.2, Five particle hypotheses is made; the simple B field and materials is updated with BESIII’s.Passed the testing by the MC data: MdcFakeData & MdcFastTrkAlg.
Status of dE/dx Module
The Codes passed the MC test and migrated to BOSS 4.2
Different algorithms and truncation ratio are studied
Calibration Const. retrieved from DB, package in design Corrections studied and par. to be optimized further
Resolution curve with different truncation rates
70% truncation ratio is adopted for the algorthm
Number of good hits is required to no less than 10 for each track
Pi/K Pi/P
0.75GeV 1.3GeV
dE/dx curve and resolution
Track Extrapolation Module Function: Extrapolate MDC tracks to Outer detectors: TOF, Coil, EMC, MUC Algorithm: based on GEANT4, Energy loss and Magnetic field. Multiple scattering effect put into error matrix.
Status TOF Reconstruction Module
TofSys
BTofSys
ETofSys
BTofMod BTofCnt
BTofScint
BTofPhotoTube
ETofCnt
ETofScint
ETofPhotoTube
ETofMod
For 88 Counter
For 96 Counter
TofRec package has been developed, and runs well on the TofRec package has been developed, and runs well on the BOSS v4.1BOSS v4.1By the signal electron the primary performance is:
Time Res. 83 ps, Track Eff 100 ,
Class structure of TofRec
LAttenuation LAttenuation 3.2M
The Results of TOF Rec. Module
Tracks found by TofRec from one MDC track .
Trk Eff 100% Time resolution 83 Ps
Attenuation Length 3.2m
Status of EMC Rec.
Clustering (Make Shower)
Gamma Rec.
Matching with MDC
Pi0 Rec.
Sketch
Extrapolating from MDC track
Extrapolate MDC track
find relations between tracks and fired strips.
1. What to do ?Fired strips
2. How to do ?
Start from an extrapolated MDC track, go on extrapolating, correct direction, attach fired strips, gap by gap…
MUC Reconstruction Module
Monte Carlo Data
0.5Gev
1.0Gev
1.5Gev
Extrapolated
MDC track
Reconstructed
MDC track
• Finished the programming and preliminary testing by MC data using two way: MDC-Track Extrapolating and 2D/3D Road
• “2D/3D Road” : Tracking EF: 99%
• “Extrapolating” : Tracking EF 99%.
SummaryModule Name Status MDC Fast track Trk-Eff 99 %, x100um, z4mm , p
10MeV
EvTime MDC-Track-1 Trk-Eff 99 % , p 6MeV , x140m, z0
2 mm
MDC-Track-2 Trk-Eff 95 %, pT 5.8MeV
dE/dx PID Trk-Ext Klmfit TOF Rec. Trk-Eff 100 % , T83ps,
EMC Rec. Trk-Eff 100 % , E2%, .007rad, .008rad
MuC Rec. Trk-Eff 99 % : Design, programming & testing : Passed the MC data testing : Performance checking and Par. Optimization stage
谢谢各位专家! Thanks
Track 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.
MdcSegFinder Sequence
For every superlayer and every wire in 2nd layerform a group of 8 wires
Try 4 hit pattern for this groupCall tryPatterns()
Try 3 hit pattern for this groupCall tryPatterns()
Set massage of segment list
Sequence of segFinder::createSegs()
For every group
4 3
2
1 0
7 6 5
10101001
01234567
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.
Performance of EMCRec(1)
E 1.85 –1.95%
• The Code EmcRec has finished the design, programming and passed the MC data testing in the BOSS V4.0 (signal photon with energy 0.5, 1.0 1.5 2.0 Gev)
• Performance: Eff: 100%
0.004 –0.007 rad
0.004 –0.008 rad
0.004 –0.007 rad
0.004 –0.008 rad
E 1.85 –1.95%
S-Z calculation in Z finding
Li sts of axi al hi ts andstereo hi ts
Conformal Transformation
Fi nd segments for each superl ayer(SL) wi th hi stogram of hi t
wi res’ azi muthal angle
Li nk segments
Parti al l y sol ve LR ambi gui ty of al l hi twi res usi ng nei ghbor wi res’ i nfomati on
Fi nd the best segment l i ststart wi th a seed i n outmost SL
Ci rcl e Fi t
Remove bad segmentCi rcl e fi t agai n
Sol ve LRCi rcl e fi t agai nCheck the qual i ty
ok
no
ok
no
Li st of R-phi Tracks
Sal vage other axi alsegments and hi ts
Ci rcl e fi tAppend to 2D track l i st
Assign shared segment or hi t
Make l i st of stereo segments usinghi stogram
Roughly sel ect segments wi thcross points of
r-phi track through SL
Cal culate (s,z) of hi tsand append them to zLi st
Take one s-z l i ne as a seed
Make possibl e s-z l i nes wi th hi ts i n zLi st(fi rst make the l onger)
ok
no
ok
no
Li st of s-z l i nes
Take a hi t i n zLi st
Whether hi t belong toseed
Append to seed
Select one of r-phiTrack Candidates
Qual i ty check for seed l i ne
Take the l ongestLine fi t
Cal culate (s,z) of hi ts
3D Hel i x Fi t
Fig.6 Flow of R-phi track finding(left) and z finding(right)
Status MDC Tracking Module (2)p 20 MeV
z0 14 mm
D0 500mTRK Eff 95%