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TrackFixup

TrackFixup. Motivation Evaluation of existing tracks Goals of TrkFixup Functional description Algorithm overview Status and plans. TrkFixup Motivation. Tracks are the core of BaBar analysis Precisely reconstruct P, trajectory of charged particles

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TrackFixup

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  1. TrackFixup David Nathan Brown Motivation Evaluation of existing tracks Goals of TrkFixup Functional description Algorithm overview Status and plans

  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 • We may never reprocess from raw data again • There is room for improvement in BaBar tracking David Nathan Brown 2 BaBar Collab. Meeting December 13, 2005

  3. MC True Charged Particles • 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 inout Momentum (GeV) Cos() David Nathan Brown 3 BaBar Collab. Meeting December 13, 2005

  4. The Truth about Reconstructed Tracks CT=‘Default’ TrkRecoTrk GTVL=|d0|<1.5cm && |z0| < 10cm 92% 8% 11% 21% 2% 90% 7% 5% 6% 1% Gev Gev 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 80% 5% 3% 4% 0% Gev David Nathan Brown 4 BaBar Collab. Meeting December 13, 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 BaBar Collab. Meeting December 13, 2005

  6. 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 David Nathan Brown 6 BaBar Collab. Meeting December 13, 2005

  7. 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 David Nathan Brown 7 BaBar Collab. Meeting December 13, 2005

  8. TrkRecoTrk Vertex Reconstruction • Primary Vertex reconstruction • Same algorithm as Beta vertexing • Comparable resolution • Vx ~ 70 m, pull width ~ 1.3 • V0 reconstruction • Uses TrkPocaVtx • W. Hulsbergen • Finds Ks,  • Efficiency >90% • Purity ~ 90% W. Hulsbergen T.Tanabe (LBL/UCB) Run3 BSemiExclusive David Nathan Brown 8 BaBar Collab. Meeting December 13, 2005

  9. TrkHitFix - Remove bad hits Preselect tracks with fit probability < 10-5 Disable <= 3 hits with residual/error> 8 Kerstin Tackmann, LBL/UCB

  10. TrkHitFix Improves Pt resolution Remove DCH hit Remove SVT hit Fraction of selected tracks With  pull < 5  1/Pt Kerstin Tackmann, LBL/UCB

  11. dE/dx constraint • 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 combined curvature David Nathan Brown 11 BaBar Collab. Meeting December 13, 2005

  12. 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 TSHA No TSHA N SVT hits reco-MC E. Prencipe David Nathan Brown 12 BaBar Collab. Meeting December 13, 2005

  13. Ghost Tracks • Ghost = 2nd track reconstructed from the same physical (charged) particle, excluding loopers  view z view David Nathan Brown 13 BaBar Collab. Meeting December 13, 2005

  14. Ghost ‘Reconstruction’ • 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 ghost Ghost David Nathan Brown 14 BaBar Collab. Meeting December 13, 2005

  15. 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. Looper Pairs (and Triples) Gerry Lynch David Nathan Brown 15 BaBar Collab. Meeting December 13, 2005

  16. Which Looper Track is Primary? Gerry Lynch David Nathan Brown 16 BaBar Collab. Meeting December 13, 2005

  17. Junk ‘Reconstruction’ Ghosts Hard Scatters Combined ~1 Track/event 2-Track Decays Transverse Radius (cm) David Nathan Brown 17 BaBar Collab. Meeting December 13, 2005

  18. 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! David Nathan Brown 18 BaBar Collab. Meeting December 13, 2005

  19. Preliminary Results 92% 8% 11% 21% 2% 80% 5% 3% 4% 0% 90% 7% 5% 6% 1% Existing 92% 8% 7% 18% 2% 91% 5% 3% 4% 0.5% 89% 5% 3% 4% 0.5% TrkFixup David Nathan Brown 19 BaBar Collab. Meeting December 13, 2005

  20. 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 D. Lopes-Pegna Standard TrkFixup David Nathan Brown 20 BaBar Collab. Meeting December 13, 2005

  21. 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? • MiniMini reprocessing followed by skim? David Nathan Brown 21 BaBar Collab. Meeting December 13, 2005

  22. 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 David Nathan Brown 22 BaBar Collab. Meeting December 13, 2005

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