Download - TrackFixup (overview)

David Nathan Brown

TrackFixup (overview)

MotivationEvaluation of existing tracksConceptual design of TrkFixupFunctional descriptionAlgorithm overviewLoop branch filter (Gerry Lynch)Phyics evaluation tools (David Lopes Pegna)Schedule Discussion

David Nathan Brown 2 Tools Workshop October 1, 2005

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


MC True Charged Particles

14% track-findinginefficiency

(18.3.1b, B generic + semi-leptonic)

Momentum (GeV) Cos()

2-3% (absolute) improvement possible

Recoverable tracks are not ‘junk’


The Truth about Reconstructed Tracks

=‘Default’ TrkRecoTrk =|d0|<1.5cm && |z0| < 10cm

= GTVL && 0.1<Pt<10.0Gev && NDch>=20

‘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

90%10%

8%20%

2%

89%8%2%6%1%

78%6%1%3%0%

Gev

Gev Gev


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 momentumRecover 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


TrkRecoTrk Lists

‘Default’List

‘Work’ List

‘Merged’List

‘Junk’ List

‘Good’ List

TrkHitFix…

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TrkLoopFix ‘Inner’

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‘Outer’List


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)


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


TrkRecoTrk Vertex Reconstruction

T.Tanabe (LBL/UCB)

Run3 BSemiExclusive

V0 reconstruction

Uses TrkPocaVtx W. Hulsbergen

Finds Ks, Efficiency >90% Purity ~ 90%

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are needed to see this picture.

W. Hulsbergen

Primary Vertex reconstruction

Uses same algorithm as Bta vertexing

Comparable resolution Vx ~ 70 m, pull width ~

1.3

Kerstin Tackmann, LBL/UCB

TrkHitFix - Method

Preselection:Track probability < 10-5

Worst hit: > 8

Disable worst hitand refit track


TrkHitFix - Results

Worst hitin DCH

Worst hitin SVT

log10trackprobability

Fraction of tracks with pull < 5


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


dE/dx constraint

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M. Battaglia

UCB/LBL

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

curvature

dE/dx

combined

Hist = before constraintPoint=after constraint


Ghost Tracks Ghost = 2nd track reconstructed from the same physical (charged) particle, excluding loopers

view z view


Ghost ‘Reconstruction’

ghos

t

ghos

t

ghos

t

ghos

t

ghos

t

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tPrimaryGhost


Ghost Selection Composition

PrimaryGhost

>90% pure

<50% efficient

Junk Ghost

Put ‘Ghost’on ‘Outer’ list

cm cm


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