TrackFixup

David Nathan Brown

TrackFixup

MotivationEvaluation of existing tracksGoals of TrkFixupFunctional descriptionAlgorithm overviewStatus and plans

David Nathan Brown 2 BaBar Collab. Meeting December 13, 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 We may never reprocess from raw data again

There is room for improvement in BaBar tracking


MC True Charged Particles

Momentum (GeV) Cos()

14% of physics tracks are not reconstructed Low momentum Outside angular coverage

2-3% efficiency in principle recoverable Requires a dedicated ‘short’ track finder, working inout


The Truth about Reconstructed Tracks

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

GTL= 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

92%8%

11%21%

2%

90%7%5%6%1%

80%5%3%4%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


How it works TrkFixup runs as part of BetaMiniSequence

cache mode questionable tracks are ‘promoted’ to a full Kalman fit

Roughly double the time of normal cache mode event read Downstream modules see full reconstruction information (TrkRecoTrk)

Dedicated modules address specific problems Loopers, pat. Rec., …

Output consists of Many track lists Inner Tracks coming from IP Outer Tracks exiting the tracking volume Loops, Ghosts, Decays, …

TrkFixupSequence is transparent to downstream modules Track-cluster match, BtaCandidate creation, …

But NOT Dirc, Ifr reconstruction Incompatible with persisted composites

A daughter track might get changed/removed


TrkFixup Algorithm Status Infrastructure

TrkRecoTrk vertexing W. Hulsbergen Mature V0 reconstruction T. Tanabe Mature

Algorithm modules under development Looper removal G. Lynch Mature Ghost track removal D. Brown Mature dE/dx momentum constraint M. Battaglia In Development

Hit filtering K. Tackmann Mature Svt hit recovery E. Prencipe In Development

Short-track recovery Open Albedo removal Open Kink finding Open Material interaction Open Bremstrahlung recovery Open


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

TrkRecoTrk Vertex Reconstruction

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

T.Tanabe (LBL/UCB)

Run3 BSemiExclusive

V0 reconstruction

Uses TrkPocaVtx W. Hulsbergen

Finds Ks, Efficiency >90% Purity ~ 90%

W. Hulsbergen

Primary Vertex reconstruction

Same algorithm as Beta vertexing

Comparable resolution Vx ~ 70 m, pull width ~

1.3

Kerstin Tackmann, LBL/UCB

TrkHitFix - Remove bad hits

Preselect tracks with fit probability < 10-5

Disable <= 3 hits with residual/error> 8

Kerstin Tackmann, LBL/UCB

TrkHitFix Improves Pt resolution

RemoveDCH hit Remove

SVT hit

Fraction of selected

tracks With pull < 5

1/Pt


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


SVT Hit Recovery Reco hit adding has cuts

to prevent adding Svt hits on V0 (Ks) daughters Induces significant hit

inefficiency Rerun TrkSvtHitAdder in

TrkFixup Select tracks with missing

inner Svt hits explicitly filter out the

V0 daughter tracks Add mini ‘unassigned’ hits

Promising early results! Needs tuning before

deployment

reco-MC

N SVT hits

E. Prencipe

TSHANo TSHA


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

view z view


Ghost ‘Reconstruction’

ghos

t

ghos

t

Gho

st

Compare of tracks at POCA

Compute average residual of DCH hits on one track to the other

Remove track branch with no Svt hits

~90% efficient, ~2% fakes


Looper Pairs (and Triples)

In the looper at the right,Track 1 is primary.

Tracks 1 and 2 form an apogee pair.

Tracks 2 and 3 form a perigee pair.

Gerry Lynch


Which Looper Track is Primary?

Gerry Lynch


Junk ‘Reconstruction’

Transverse Radius (cm)

Ghosts

Hard Scatters

2-Track Decays Combined~1 Track/event


Emc Cluster Matching Rerun EmcTrackMatch in TrkFixup

All necessary information is available in ‘cache’ mode

Slightly modified algorithm to use TrkRecoTrk, not EmcTrkInterInfo

Use the ‘Outer’ list of tracks for cluster matching Removes Ghost tracks and other fakes Removes mother track of decay-in-flight, etc Keeps decay daughters, mat. Int. daughters, ….

Small changes in performance ~1% increase in photon rate ~2% increase in fake photon background

Fewer background clusters wrongly associated to tracks

More study and tuning necessary!


Preliminary Results92%

8%11%21%

2%

90%7%5%6%1%

80%5%3%4%0%

92%8%7%

18%2%

91%5%3%4%

0.5%

89%5%3%4%

0.5%


BSemiExcl ‘Best B’ BSemiExcl skim run with/without TrkFixup Choose Best B based on purity 30% increase in efficiency

Signal peak is 10% wider Decreased background under the peak

Standard TrkFixup

D. Lopes-Pegna


TrkFixup Deployment Plans 19-series Release with functional TrkFixup imminent sourceFoundFile TrkFixup/TrkFixupDirect

Start understanding physics impact in January 2006 D. Lopes-Pegna coordinating work with AWGs

Algorithm development through spring 2006 Final physics impact studies AFTER winter conferences

TrkFixup production in summer 2006 Dedicated skim cycle? MiniMini reprocessing followed by skim?


Conclusions BaBar tracking can be improved

Existing algorithms predate Wired, mini, CM2 Improvements produce more physics/fb-1

TrkFixup refines BaBar tracking for analysis Addresses residual reco problems Improves ‘junk’ filtering by addressing specific issues

A core of TrkFixup is now available for testing Several mature modules A preliminary analysis interface Promising early results

Development continues Interesting projects are still available

Production deployment is forseen for Spring/Summer 2006

Documents

TrackFixup