Track reconstruction and hyperon simulations

1. Track reconstruction and hyperon simulations Evgeny Kryshen (PNPI, SPbSPU)

2. Analysis strategy and simulation of STS detector inefficiencies Impact of STS detector inefficiencies on tracking Tracking performance for 8 station setup Impact of STS detector inefficiencies for 8 station setup Tracking performance for 9 station setup Replacing hybrid stations with strips Studies of the half-length strip configuration Conclusions and outlook Outline CBM Collaboration meeting

3. No pile-up in MAPS stations is assumed “Realistic” station thickness and strip pitch 1 level of the the CA track finder (primary search) Statistics: 100 central 25 GeV UrQMD events Active shielding field map Performance criteria: Tracking performance - all tracks Tracking performance - primaries Tracking performance – lambda (2 level – all search) Momentum resolution Time consumption Analysis strategy CBM Collaboration meeting

4. “Realistic” geometry vs CVS CVS geometry (sts-3maps-4strips.geo + sts_digi.par): Type: Z Position: Thickness: Resolution: Maps 5,10 cm 100 μm sigma = 5 μm Hybrid 20 cm 100 μm pixel size = 50 μm Strips 40,60,80,100 cm 200 μmpitch = 25 μm “Realistic” geometry (sts-2maps-1pix-4strips.geo + sts_digi_50.par): Type: Z Position: Thickness: Resolution: Maps 5,10 cm 150 μm sigma = 5 μm Hybrid 20 cm 700 μm pixel size = 50 μm Strips 40,60,80,100 cm 400 μmpitch = 50 μm CBM Collaboration meeting

5. Hit efficiency is already implemented in MAPS hit producer (flag = -1 in the case of lost hits) Hybrid pixel hit efficiency was added into Hybrid pixel hit producer Strip efficiency is added for each side of the strip station In the present analysis equal efficiency rate is set for all detector types Efficiency simulation CBM Collaboration meeting

6. Tracking vs STS efficiency • CA track finder performance is almost the same: • AllSet: 0.89 -> 0.87, • RefSet: 0.97-> 0.94 CBM Collaboration meeting

7. Type:Z Position:Thickness: Maps 5,10 cm 150 μm Hybrid 20,30 cm 700 μm Strips 40,60,80,100 cm 400 μm 8 station geometry Geometry: sts-2maps-2pix-4strips.geo Strips: sts_digi_50_5-8.par CBM Collaboration meeting

8. Track reconstruction with 8 STS stations Statistics: 100 events At 99% STS hit efficiency Advantages of the 8 station: • significant increase (12%) in the number of reconstructed tracks • less calculation time • 60% increase in the number of reconstructed Lambda decays • More stable to STS hit inefficiencies • 2 times lower ghost rate Disadvantages of the 8 station: • increase in clones rate (1.4  6.7) • decrease in momentum resolution (1.00%  1.18%) CBM Collaboration meeting

9. Tracking vs STS efficiency (7 or 8 stations) • 8 stations – better resistance to the STS hit inefficiency CBM Collaboration meeting

10. Momentum resolution vs STS hit efficiency Worse momentum resolution: 8 stations – 1.14 % 7 stations – 0.97 % Possible solution: use strip stations CBM Collaboration meeting

11. Ghosts and clones (8 stations) • Advantages of the 8 station: • Lower ghost rate • Better resistance to the STS inefficiency CBM Collaboration meeting

12. 9 STS stations Problem: what could we gain from the additional 9th station? Type:Z Position:Thickness: Maps 5,10 cm 150 μm Hybrid 20,30 cm 700 μm Strips 40,55,70,85,100 cm 400 μm Geometry: sts-2maps-2pix-5strips.geo Strips: sts_digi_50_5-9.par Additional strip station inserted. 5 equidistant strip stations are parameterized with the usual sector geometry applying simple sector scaling CBM Collaboration meeting

13. Track reconstruction with 9 STS stations Statistics: 100 events At 99% STS hit efficiency Advantages of the 9 station: • slight increase (2%) in the number of reconstructed tracks • 40% increase in calculation time performance • 40% increase in the number of reconstructed Lambda decays • More stable to STS hit inefficiencies Disadvantages of the 9 station: • increase in ghost rate (13.2  15.6) • increase in clones rate (6.7  11.4) • decrease in momentum resolution (1.18%  1.32%) CBM Collaboration meeting

14. Strips vs hybrids (7 station setup) • Do we need the third technology (hybrid pixels)? What we get when replacing hybrids with strips? • 6% decrease in the number of rec. tracks • Small gain in momentum resolution • 2 times higher ghost rate • 3rd hybrid station (700 μm) replaced with strip station (400 μm). • Simple scaling of strip sector geometry (minimum strip length – 1 cm) CBM Collaboration meeting

15. Strips vs hybrids (8 station setup) • Can we achieve better momentum resolution by replacing hybrids (700 μm) with strips (400μm)? • 10% decrease in the number of rec. tracks • 0.08% gain in momentum resolution • 4 times higher ghost rate • 3 and 4 hybrid stations (700 μm) replaced with strip stations (400 μm). • Simple scaling of strip sector geometry (minimum strip length – 1 cm) CBM Collaboration meeting

16. Strips vs hybrids (9 station setup) • Can we achieve better momentum resolution by replacing hybrids (700 μm) with strips (400μm)? • 8% decrease in the number of rec. tracks • 0.08% gain in momentum resolution • 3.5 times higher ghost rate • 3 and 4 hybrid stations (700 μm) replaced with strip stations (400 μm). • Simple scaling of strip sector geometry (minimum strip length – 1 cm) CBM Collaboration meeting

17. Half-length strip parametrization CBM Collaboration meeting

18. 7 station setup is quite sensitive to the STS inefficiencies 8 station setup allows to improve track reconstruction performance significantly, the only drawback – lower momentum resolution 9 station setup – slight improvement in track reconstruction performance, further increase of reconstructed lambda Hybrid stations are desirable in respect to the track finding CPU consumption is very sensitive to the number and type of STS stations Reduction of strip length does not provide a significant gain in track reconstruction New “realistic” sector geometry (J. Heuser) to be tested Conclusions and outlook CBM Collaboration meeting