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Overhauling the STAR Reconstruction: Updates on ITTF, TPC Tuning, and SVT Integration

The Integrated Tracking Task Force (ITTF) is replacing the outdated Fortran tracker with the Integrated Tracking Package (Sti) to enhance our reconstruction chain's efficiency. This summer, tuning efforts for the Time Projection Chamber (TPC) commenced, supported by essential diagnostics and comparisons with previous data. We aim to automate the tuning process, focusing on improving track efficiency and minimizing inaccuracies. Additionally, we are integrating the Silicon Vertex Tracker (SVT) and addressing performance disparities. Regular updates and tuning progress can be followed through provided links.

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Overhauling the STAR Reconstruction: Updates on ITTF, TPC Tuning, and SVT Integration

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  1. Reminder • ITTF - Integrated Tracking Task Force • Integrated Tracking Package - “Sti” • Replacement for current Fortran based tracker • Run IV: • Together with DAQ100, really means STAR is undergoing an overhaul of our whole reconstruction chain!

  2. TPC Tuning in Summer • A. Rose began tuning effort • Instructions for tuners: • http://www.star.bnl.gov/STAR/ittf/HOWTO/ITTF_Tuning.html • Results from summer: • http://www.star.bnl.gov/~andrewar/ITTF/Tuning.html Efficiency for central events

  3. Diagnostics, Pulls… • Change parameters • Check efficiencies • Check pulls • Curvature • Tan l • Repeat… • Thanks to Andrew had a good set of parameters already

  4. TPC Tuning currently • B. Hippolyte (originally signed up for SVT tuning) • Lots of work to automate the tuning process • Double check residuals • compare to Fabrice’s and Andrew’s results • Compare Sti to Tpt residuals • Tuning with real data • Baseline: use previous tracker and make comparisons http://www.star.bnl.gov/protected/strange/hippolyt/Tuning/tuning.html

  5. Boris’s comparisons

  6. Ratio STI/TPT for Global Dca and PT distributions Ratio > 1 so STI is more efficient… if splitting is not a problem. Global DCA with # fit hits > 39 Global DCA with # fit hits > 14 pT with # fit hits > 14 B. Hippolyte

  7. Splitting/Merging • Thanks Mercedes! • Q: Does track excess come from splitting? • Boris + Mercedes, blind test • 3 sets of data, one with large window • Mercedes finds splitting in that set (blind test) • Does not find splitting in the others! • A: They don’t! • Merging: • Significant number of pairs with low q but large “entrance separation” • Possble explanation: primary track cuts were open • http://www.star.bnl.gov/protected/hbt/mercedes/ITTF/Jan04.html

  8. Svt Tracking Performance Comparison • THANKS to Helen and Marcelo for helping smooth out remaining issues with ITTF & Svt • Svt tuning currently ongoing (Sevil) • Code changes to SVT code in Sti: • Geometry fixes, selection of hits using SVT flags • Mainly cosmetic changes (but they add up!)

  9. Svt Hits • ITTF and EST • N MC Svt Hit >0 • Mc Pt >.3 GeV/c • -.5 < eta < .5 • 10 < N MC Tpc Hits < 55 • “Common Hit” study • hits shared by MC track and reconstructed track • Est has better matching; • (Common spectrum peaks higher) • ITTF Untuned; should only get better ITTF EST no information on EST N Rec Svt Hits

  10. Efficiency and Purity, differences • Efficiency of adding the right hits Monte Carlo – Common = number ofrightpoints do youmiss • Purity of hits added N Fit – Common = number of points on track that arewrong (ie, not from matched track) ITTF EST Missed hits ITTF • Cuts: • N MC Svt Hit >0 • Mc Pt >.3 GeV/c • -.5 < eta < .5 • 10 < N MC Tpc Hits < 55 Wrong hits

  11. Efficiency and Purity, ratios • Efficiency of adding the right hits: Common / MC = Fraction ofrighthits found • Purity of hits added: Common / nFit = Fraction of hits on track that areright ITTF EST ITTF • Cuts: • N MC Svt Hit >0 • Mc Pt >.3 GeV/c • -.5 < eta < .5 • 10 < N MC Tpc Hits < 55

  12. Performance vs. MC Hit Cuts: • N MC Svt Hit >0 • Mc Pt >.3 GeV/c • -.5 < eta < .5 • 10 < N MC Tpc Hits < 55 • Efficiency • ( N Common vs MC) Similar for EST and ITTF • ITTF Svt Pts (blue) • indicate impurity • to be addressed through tuning

  13. SVT Status • ITTF Successfully Matching to Svt in Monte Carlo, at the level expect for the current tune parameters • hit error ~1mm, large search window (can lead to impurity) • ITTF and EST show similar trends for finding the correct hit, and fraction of correct hits found. • EST is slightly better. • ITTF is not pure • adds incorrect hits at a rate of ~35% (over all mult.). • Should improve with realistic hit errors (~150m) and tune parameters.

  14. Other Integration issues • Claude, Yuri, Michael, working on DB integration • Geometry is loaded from db • Using bfc can pick up the right time-stamp • Tracking parameters kept in db for production • Allows to document what was used for a given production • Claude also implemented a solution for quick reading of parameters for tuners • Lee, working on Vertex integration • Comparions… • Old tracks-new vertex finder • New tracks-new vertex finder

  15. Plan for Final Approach to Integration • Experience with last “crash-effort” meeting was encouraging. • Work got done, communication is better in person. • Big pieces of the to-do list were dealt with • Need to focus now on getting the pieces working together. • Still tasks to do. Jerome proposes another “crash” meeting • March 15 - code is frozen and moved to ‘new’ • ‘dev’ becomes the test-bed for integration crash-effort

  16. Next crash-effort • Goal: finalize a production version of bfc. • Begins with a daq file • Creates a minimal StEvent (Trigger Info mainly) • Hits are filled into StEvent • TPC (fcf, StTpcHitMoverMaker), SVT, FTPC • Tracking in Sti • Global tracking pass, filling of StGlobalTracks • Call to vertex finder • Primary tracking pass, filling of StPrimaryTracks • V0, X, Kink finders, (C++ , StEvent based) • Sub-system reco software, dEdx, etc.

  17. Additional Slides…

  18. ITTF Last Review: Computing Resources • Memory Footprint • Up to 7000 Tracks in a central event, • Up to 55 Hits/track. • Footprint < 350MBytes • Tracking time • Scale linearly with number of tracks • Central Au+Au : 10 s. • ~ 5 faster than previous STAR tracker

  19. ITTF Last Review: Efficiencies vs pt OPEN Cuts : MC Hit > 10 -1<h<1 DCA<3 ITTF (new tracker) TPT(old tracker) High Multiplicity Low Multiplicity Pt (GeV/c) Pt (GeV/c)

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