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TRD and Global tracking

TRD and Global tracking. Andrey Lebedev GSI, Darmstadt and LIT JINR, Dubna Gennady Ososkov LIT JINR, Dubna. X CBM collaboration meeting Dresden, 27 September 2007. Contents. TRD tracking Improvements of algorithms Current status of TRD tracking efficiencies Layout studies

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TRD and Global tracking

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  1. TRD and Global tracking Andrey Lebedev GSI, Darmstadt and LIT JINR, Dubna Gennady Ososkov LIT JINR, Dubna X CBM collaboration meeting Dresden, 27 September 2007

  2. Contents TRD tracking Improvements of algorithms Current status of TRD tracking efficiencies Layout studies Global tracking Performance Conclusions and outlook

  3. Improvements of algorithms To optimize tracking routine some parameters should be specified on each iteration. They are: sigma coefficient, which determines prediction corridor station to begin the search, end station, maximum number of missing hits in station to admit, etc. Recall of the tracking procedure: it started from either prolonging tracks from STS to the 1st TRD layer, or in standalone version from combinatorial search for track elements in the 1st station. obtained track-elements are propagated through the station and pick up the hits according to 4 main parameters listed above In order to decrease combinatorics it is reasonable to realize this procedure in several iterations, as it it depicted in table below: Iteration\Parameter Sigma coefficient Begin station End station Nof missing hits 1 3 1 3 0 2 5 1 2 0 3 5 2 3 0 4 5 1 3 1

  4. Improvements of software To realize this, software was partly redesigned and some functions were optimized: • Tracking improvements listed above. • Runge-Kutta 4th order with adaptive step size control was implemented. • The code of Kalman Filter procedures was optimized to get them faster.

  5. TRD tracking efficiencies STS->TRD tracking Standalone TRD tracking • Standard TRD geometry with 3 stations and 4 layers per station. • 500 central Au-Au events at 25 GeV. Standalone motivation: • Search for tracks missed in the STS • As a J/Psi trigger

  6. TRD layout studies The basic idea of this study is minimising the costs of the detector. What is the optimal layout for the tracking? What is the minimum number of TRD stations/layers? Costs vs. tracking performance. 4-4-4 Standard setup 3-3-3 25% saving Standalone TRD tracking is not available now for these layouts. 2-2-2 50% saving 4-2-2 34%saving 4-3-3 17%saving

  7. TRD layout study [thin/thick layout] • Thin and thick layers were used for each of the TRD setups, shown before • Each detector layer consist of the following layers: • a 29/30 mm thick radiator made out of polypropylene • a 6/6 mm thick gas layer made out of a gas which is defined in media.geo • a backplane which consist of the following parts to mimic the material budget of a real backplane • a 0.03/0.05 mm padplane made out of gold coated copper • a 1.5/2.0 mm thick layer made out of mylar • a 0.07/0.1 mm thick layer made out of gold coated copper red – thin blue - thick

  8. TRD layout studies [STS->TRD tracking] Efficiencies for different TRD geometries. STS->TRD tracking. thin/thick thin thick geometry 2-2-2 3-3-3 4-4-4 4-2-2 4-3-3 2-2-2 3-3-3 4-4-4 4-2-2 4-3-3 all, % 95.7 95.2 95.5 95.5 95.5 95.5 94.8 95.2 95.3 95.4 vertex, % 95.9 95.4 95.6 95.7 95.7 95.6 95.0 95.4 95.4 95.5 reference, % 96.3 95.7 95.8 96.0 95.9 96.0 95.3 95.6 95.8 95.8 secondary, % 94.1 93.4 93.9 93.8 93.9 94.0 93.3 93.6 93.8 94.1 ghost, % 5.8 5.2 3.7 4.1 3.2 6.3 6.0 4.2 4.6 3.8 rec. tracks 459 448 438 447 442 457 446 437 447 441 good tracks 434 426 423 430 429 431 421 420 428 426 good w/o STS 11 11 11 10 11 11 12 12 12 12 ghost 24 21 15 17 13 27 25 17 19 15 clone 0 0 0 0 0 0 0 0 0 0 time, sec/event 0.4 0.6 0.8 0.6 0.7 0.4 0.6 0.9 0.6 0.7 • Tracking performances for different TRD layouts look surprisingly the same. • Efficiency at the level of 95-96%. • Ghost rate slightly higher for thick detector setup. • Note: keep in mind that such conclusion relates only to tracking performance without the study of electron-pion separation and other physical conclusions. 500 central Au-Au events at 25 GeV.

  9. TRD layout studies [TRD standalone tracking] Efficiencies for different TRD geometries. Standalone TRD tracking. thin/thick thin thick geometry 4-4-4 4-2-2 4-3-3 4-4-4 4-2-2 4-3-3 all, % 89.1 88.8 88.9 89.0 88.5 88.9 vertex, % 94.3 94.6 94.3 94.1 94.2 94.1 reference, % 94.4 94.7 94.4 94.3 94.5 94.3 secondary, % 77.1 75.8 76.6 77.1 75.7 77.0 ghost, % 6.2 7.1 5.9 7.5 8.2 7.0 rec. tracks 640 669 652 642 670 653 good tracks 600 621 614 594 615 607 ghost 40 48 39 48 55 46 clone 0 0 0 0 0 0 time, sec/event 2.0 0.7 1.2 2 0.8 1.2 • Tracking performances for different TRD layouts look also similar. • Efficiency at the level of 89%. 500 central Au-Au events at 25 GeV.

  10. Efficiencies for different normalizations Efficiencies dependence on the minimum number of points for accepted tracks for standard TRD geometry (4-4-4, thin layout) Nof points ≥6 ≥8 ≥10 ≥12 all 93.8 (412/439) 94.6(408/431) 95.4(394/413) 95.5 (389/406) vertex 93.9 (377/402) 94.7 (374/395) 95.6 (361/378) 95.6(355/371) reference 94.5 (330/349) 95.2 (327/344) 95.8 (317/331) 95.8 (312/326) secondary 92.3 (34/37) 93.1 (34/37) 93.8 (33/35) 93.9 (33/35) ghost 3.4 (15/439) 3.5 (15/431) 3.6 (15/413) 3.7(15/406) reconstructed TRD tracks 438 good TRD tracks 423 good TRD tracks w/o STS track 11 ghosts 15 clones 0 • Efficiency doesn’t change a lot for different normalizations • The tracking algorithm is able to find also a short tracks, which are not pass through the whole detector or tracks which have a missing hits (should be tested more carefully after the implementation of the detector inefficiencies in TRD) 500 central Au-Au events at 25 GeV.

  11. Performance [global tracking] STS + TRD STS + TRD + TOF Eff=79% Eff=85% Tools: • L1 tracking for STS • Lit STS->TRD tracking, no actually merging between STS and TRD tracks • TOF merger by the closest distance

  12. Summary and outlook • TRD tracking improvements have been done and lead to the performance gain. • Layout study for both TRD tracking algorithms has shown quite similar results for different TRD setups even if the number of layers twice decreased. However, keep in mind that such conclusion relates only to tracking performance without the study of electron-pion separation and other physical conclusions. • Global tracking results obtained for current CBM setup looks good. • Outlook • Continue the studies concerning the optimal TRD layout, including also global tracking efficiency. • For the global tracking: compare 2 tracking approaches: • STS based TRD tracking • standalone TRD tracking plus track merging • MUCH tracking

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