1. TrackFixup (overview)
David Nathan Brown
Motivation
Evaluation of existing tracks
Conceptual design of TrkFixup
Functional description
Algorithm overview
Loop branch filter (Gerry Lynch)
Phyics evaluation tools (David Lopes Pegna)
Schedule Discussion

2. TrkFixup Motivation Tracks are the core of BaBar analysis
Precisely reconstruct P, trajectory of charged particles
Implicitly define neutral particles (= clusters with no track)
Track efficiency is combinatoric in most analyses
Small improvements can have important net results
Improved tracking efficiency = ‘free luminosity’
Especially relevant in competing with Belle
The Mini contains detailed detector-level information
Allows running ‘reconstruction’ algorithms in analysis
The existing track selections predate the mini
The next full reprocessing will be in ….
There is room for improvement in BaBar tracking
David Nathan Brown 2 Tools Workshop October 1, 2005

3. MC True Charged Particles
(18.3.1b, B generic + semi-leptonic)
14% track-finding
inefficiency
Momentum (GeV)
Cos()
2-3% (absolute) improvement possible
Recoverable tracks are not ‘junk’
David Nathan Brown 3 Tools Workshop October 1, 2005

4. The Truth about Reconstructed Tracks
=‘Default’ TrkRecoTrk
=|d0|<1.5cm && |z0| < 10cm
90%
10% 8%
20% 2%
89% 8% 2% 6% 1%
Gev
Gev
= GTVL && 0.1<Pt<10.0Gev && NDch>=20
78% 6% 1% 3% 0%
‘good reco’  2 (reco-true params)<100
‘bad reco’  2 (reco-true params)>100
‘duplicates’  ghosts, loopers,…
‘Phys. Bkg.’  decay-in-flight, …
‘Det. Bkg.’  mat. Int., albedo, …
‘Machine Bkg.’ Background frame
Gev
David Nathan Brown 4 Tools Workshop October 1, 2005

5. TrkFixup Goals Increase the track finding efficiency
Recover tracks with >= 4(6) Svt hits
Improve track resolution (good track efficiency)
Cleanup pat. rec. errors
Accommodate non-Gaussian effects
hit resolution, hard scattering, …
Add information to the track fits
dE/dx constraint on momentum
Recover lost (inner) Svt hits
Filter ‘Junk’ tracks explicitly by process
Duplicate tracks (loop branches, ghosts, …)
Physics and detector background (kinks, had. Int., …)
Machine background (svt only random combinations)
Define ‘physics lists’ of TrkRecoTrk objects
Standardized pre-selection for analysis
David Nathan Brown 5 Tools Workshop October 1, 2005

6. … TrkRecoTrk Lists duplicate candidate: Promote to Kalman fit
‘Bad’ track fits or
‘Work’ List
‘Inner’
List
TrkHitFix
TrkLoopFix …
‘Merged’
List
‘Default’
List
‘Outer’
List
Good track fits,
No duplicates:
Set aside
‘Junk’ List
‘Good’ List
David Nathan Brown 6 Tools Workshop October 1, 2005

7. How it works TrkFixup works on TrkRecoTrk objects
Full reconstruction interface, not Beta!
TrkFixup runs in cache mode
questionable tracks are ‘promoted’ to a full Kalman fit
Roughly double the time of normal cache mode event read
Refit mode is 10x cache mode
TrkFixupSequence is inserted into BetaMiniSequence
Before track-cluster match
BtaCandidates are rebuilt from tracks
Two possible configurations for BtaCandidate lists
Produce ‘Fixup’ lists in parallel with ‘normal’ lists
Tracks are copied (to avoid changing ‘normal’ tracks)
New lists are ‘ChargedTracksFixup’, etc.
Overwrite ‘normal’ lists (direct)
David Nathan Brown 7 Tools Workshop October 1, 2005

8. TrkFixup Algorithm Status
Infrastructure
TrkRecoTrk vertexing W. Hulsbergen
V0 reconstruction T. Tanabe
Algorithm modules under development
Looper removal G. Lynch In TrkFixup
Ghost track removal D. Brown In TrkFixup
dE/dx momentum constraint M. Battaglia In Development
Hit filtering K. Tackmann In TrkFixup
Svt hit recovery E. Prencipe In Development
Short-track recovery Open
Albedo removal Open
Kink finding Open
Material interaction Open
Bremstrahlung recovery Open
David Nathan Brown 8 Tools Workshop October 1, 2005

9. TrkRecoTrk Vertex Reconstruction
Primary Vertex reconstruction
Uses same algorithm as Bta vertexing
Comparable resolution
Vx ~ 70 m, pull width ~ 1.3
W. Hulsbergen
T.Tanabe (LBL/UCB)
V0 reconstruction
Uses TrkPocaVtx
W. Hulsbergen
Finds Ks, 
Efficiency >90%
Purity ~ 90%
Run3 BSemiExclusive
David Nathan Brown 9 Tools Workshop October 1, 2005

10. TrkHitFix - Method Worst hit: > 8 Disable worst hit
and refit track
Preselection:
Track probability < 10-5
Kerstin Tackmann, LBL/UCB

11. Kerstin Tackmann, LBL/UCB
TrkHitFix - Results
Worst hit
in DCH
log10track
probability
Worst hit
in SVT
Fraction of
tracks with
 pull < 5
Kerstin Tackmann, LBL/UCB

12. TrkHitFix - Summary and Plans
TrkHitFix module improves  resolution and track fit
probability
Largest effect in intermediate momentum region
Possible improvements:
Try to separate SVT hits in tail and bump of  pull
distribution
Allow disabling several hits
Worst hit 
Kerstin Tackmann, LBL/UCB

13. dE/dx constraint M. Battaglia UCB/LBL dE/dx curvature combined
Idea: constrain momentum using (Svt) dE/dx by inverting B.B. curve
Provides competitive P measurement as curvature at low momentum
Makes P/P ~ flat vs P at <5%
Reduces outlyers
Need improved calibration of dE/dx to go below 90Mev
M. Battaglia
UCB/LBL
Hist = before constraint
Point=after constraint
dE/dx
curvature
combined
David Nathan Brown 13 Tools Workshop October 1, 2005

14. Ghost Tracks
Ghost = 2nd track reconstructed from the same physical (charged) particle, excluding loopers
 view
z view
David Nathan Brown 14 Tools Workshop October 1, 2005

15. Ghost ‘Reconstruction’
Primary
David Nathan Brown 15 Tools Workshop October 1, 2005

16. Ghost Selection Composition
Put ‘Ghost’
on ‘Outer’ list
Junk Ghost
Primary
Ghost
<50% efficient
>90% pure cm cm
David Nathan Brown 16 Tools Workshop October 1, 2005

17. TrkGhostFix to-do Try to improve efficiency
Loosen cuts?
New selection?
Find better algorithm to define ‘Primary’ track when neither have Svt hits
Can momentum be improved by merging?
Preliminary result: no
David Nathan Brown 17 Tools Workshop October 1, 2005