MdcPatRec Tracking Status

Zhang Yao , Zhang Xueyao

Shandong University

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Outline

1. Main Drift Chamber (MDC) geometry

2. Tracking background

3. Tracking algorithm

4. Modification of algorithms

5. Tracking Performance

6. Summary

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Main Drift Chamber (MDC) geometry

Interaction point

Cosθ=0.83

Cosθ=0.93

• 43 sense wire layers group to 11 super-layer

• cosθ from -0.93 to 0.93

• Cell is nearly square in shape

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MDC Tracking software MdcPatRec

• MDC tracking software purpose– Precise momentum measurement– Efficiency find tracks short and not form IP

• Migrated from BaBar Drifit Chamber Tracking software

• Personpower

– Zhang Xueyao of Shangdong University

– Zhang Yao of Shangdong University

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MdcPatRec Tracking algorithm

Make Hits

Track Finding : 2-D tracking

Segment finding

Track Finding : 3-D tracking

MdcDigi

MdcHit

Segment

Circle

Helix

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Tracking algorithm(1) --- Segment finding

4 3

2

1 0

7 6 5

10101001

01234567

Pattern No.0

(2,0)(2,1)(2,2)(2,3)(2,4)(2,5)

(1,0)(1,1)(1,2)(1,3)(1,4)(1,5)

(3,0)(3,1)(3,2)(3,3)(3,4)(3,5)

(0,0)(0,1)(0,2)(0,3)(0,4)(0,5)

clockwise

One of segment patternOne 4-hit segment pattern

Map to a group-word to match exist pattern

We have 8 4-hit patterns and 20 3-hit patterns in all

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Tracking algorithm(2) --- Track finding

Combine axial segments

Circle fitting

Combine stereo segments

Helix fitting

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Modification of algorithm

1. MDC GeometryCreate a new interface through MdcGeomSvc to MdcPatRec

reconstruction algorithm

2. Segment constructionChange the segment construction

3. Stereo segment fittingUse new algorithm of fitting suit to MDC geometry

4. Track parameter conversionConvert BaBar tracking parameter to BesIII parameter Add

some new features to tracking result.

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• Original segment finding algorithm– construct 8 bit group-word according to one reference wire by wire Id

– But the super-layer1 ~ 5 don’t have equal numbers of cell in each layer

– The neighbors in wire Id is not the neighbors in position

– CAN NOT construct by wire id in super-layer 1~5

… … … …

Modification of algorithm(1) --- segment construction

clockwise

(2,0)(2,1)(2,2)(2,3)(2,4)(2,5)

(1,0)(1,1)(1,2)(1,3)(1,4)(1,5)

(3,0)(3,1)(3,2)(3,3)(3,4)(3,5)

(0,0)(0,1)(0,2)(0,3)(0,4)(0,5)

Referencewire

Efficiency of segment finding rely on “neighbor”s finding

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• Use φ (azimuthal angle) of reference wire get “neighbors”

• Take 2 reference wire– Layer 2 and layer 0: take No. 2 wire as reference wire

– Layer 3 : take No. 4 wire as reference wire

• Verify the shape of segment 4 3

2

1 0

7 6 5

0

1

2

3Layer id

Referencewires

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12

10

layerlayer

layerlayer

layerlayer

•All segments can pass this test•Almost all hits can form segment

Modification of algorithm(1) --- segment construction

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Modification of algorithm(2) --- stereo segment fitting

• Lost hits in stereo super-layer (especially inner chamber)

• Stereo layers don’t share rotate angle in super-layer of inner chamber

Calculate approximate z0 and cotθ by “stereo angle of super-layer”

Calculate position of every hits in super- layers, do a linear fit, get z0 and cotθ

Boss V5.0.0 New st. fitting algorithm

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Modification of algorithm(3) --- Track parameter conversion

Tbabar

babar

z

z

babar

t

babar

babar

SXSEYE

zd

Bp

dd

)()(

tantan

567.33312

0

00

0

Five helix parameters and error matrix

Other parameters of trackand hits converted for TDS

ambiguity flag left - 1 => left 0 right 1 => right 1 don’t know 0 => don’t know 2

Nstereo hits

number of hit in stereo layer

φterminal

φ of hit with max flight lengthMdcRecHit Status If hit is used in helix fitting

•Convert BaBar parameters to BesIII parameters and stored to TDS

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Tracking Performance

• Use new MDC geometry– Rotate cell number of stereo layer changed

– Number of wires in super-layer No. 6 changed

• Single track event generated by – SingleParticleGun

– fixed in transverse momentum

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Tracking Performance(1) --- New stereo fitting

Boss V5.0.0 New st fitting algorithm

•Efficiency of stereo super-layer tracking improved•Momentum resolution, spatial resolution improved

Inner chamber hits increase!

Hit distribution on layers

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Tracking Performance(2) --- spatial distribution

μ- at pt = 1GeV/cDistribution of d0

σ=0.15 mm

μ- at pt = 1GeV/cDistribution of z0

σ=0.8 mm

•d0: signed distance from the pivot to track in x-y plane•z0: signed distance from the pivot to track in z direction

Note: d0 and z0 fitted with double Gaussian

d0 (cm) z0 (cm)

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Tracking Performance(3) --- Tracking uniformity

μ- at pt = 1GeV/c, cos θ [–1 ,1], [0, 2π]

θ of Mc Truth

φ of Mc Truth

θ after recon.

φ after recon.

φ (rads) φ (rads)

θ (rads) d0 (rads)

Tra

cks

Tra

cks

Tra

cks

Tra

cks

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Tracking Performance(4) --- Momentum resolution

Note: Fitted with single Gaussian in each bin.

μ- at pt = 1GeV/cMomentum resolutionσ = 0.4%

Momentum resolution Vs Pt (e-,μ-,π,p)

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Tracking Performance(5) --- spatial residual

μ- at pt = 1GeV/cspatial residualσ = 110μm

spatial residual Vs Pt (e-,μ-,π,p)

pt (GeV/c)Note: Fitted with double Gaussian in each bin.

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Tracking Performance(6) --- Tracking efficiency for single track

Efficiency vs Pt (e-,μ-,π,p)

•Have good efficiency with decrease of Pt •Can keep efficiency with 99% at noise level of 20% with

noise type1 and type2

95% 95%95%

pt (GeV/c) Noise level (%)

Noise level type0: = C type1: 1/r type2: 1/r2

Noise level (%)

Eff

.

Eff

.

Eff

.

Efficiency vs Noisee- (type0,1,2)

Efficiency vs Noise type0 (e-,k,π-)

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Summary

1. Released in Boss 5.0.0 , can be used by analysis codes. 2. Segment tracking and stereo fitting improved3. Requirements satisfied from tracking point of view:

• Good momentum and spatial resolution : σxy = 110 μm, σ( δpt/pt ) = 0.4%. (muons)

• High tracking efficiency: efficiency > 99% for single track pt > 300MeV

• Good tracking performance at high noise level

4. Work with MDC calibration next5. Need further checking with low momentum , not form IP,

and multi-track event

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Thank you!