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Forward Tracking in a Linear Collider Detector

Forward Tracking in a Linear Collider Detector. Robin Glattauer Rudolf Frühwirth Winfried A. Mitaroff Annual Meeting of ÖPG-FAKT Univ. Graz, 18–21 Sept. 2012. P hysics motivation Experimental environment: International Linear Collider (ILC) International Large Detector (ILD)

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Forward Tracking in a Linear Collider Detector

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  1. Forward Tracking in aLinear ColliderDetector Robin Glattauer Rudolf Frühwirth Winfried A. Mitaroff Annual Meeting of ÖPG-FAKT Univ. Graz, 18–21 Sept. 2012

  2. Physics motivation • Experimental environment: • International Linear Collider (ILC) • International Large Detector (ILD) • Track reconstruction: • Strategy • Forward tracking • Performance • Summary and outlook Winni Mitaroff: ÖPG-FAKT

  3. Collisions at the TeV scale Winni Mitaroff: ÖPG-FAKT

  4. Cross sections at the TeV scale p p e–e+ Winni Mitaroff: ÖPG-FAKT

  5. Example: simulated Higgs event LHC ILC e– e+Z H Ze– e+, H b b … – Winni Mitaroff: ÖPG-FAKT

  6. The International Linear Collider (ILC) The ILC basic design is a worldwide consent since autumn 2004; Technology is based on superconducting RF cavities at 1.3 GHz, average field gradient is 31.5 MV/m in the first stages ≤ 500 GeV; The project is pursued by the “Global Design Effort” since 2005. – 3 stages: collision energies 250 GeV(“Higgs Factory”), 500 GeV, eventually 1 TeV(adjustable for scans in range 200 – 500 GeV); – Stability and precision of the beam energies to be below 0.1 %; – Peak luminosity of ≈ 2×1034 cm-2s-1, with an integrated luminosity of 500 fb-1 to be achieved within the first 4 years of operation; – Electron polarization at least 80%, positron polarization an option; – Options: Z0factory (“GigaZ”), e–e–, e–γ, γγ (“photon collider”). Beam crossing angle 14 mrad;Only 1 experimental zone with2 detectors operated in “push/pull”. Winni Mitaroff: ÖPG-FAKT

  7. The International Large Detector (ILD) • Central tracking detector: large TPC– excellent pattern recognition in a dense track environment,– proven technology; • Silicon tracker: pixels and ss/ds strips– extended tracking coverage,– improved track momentum resolution; • High-precision Si vertex detector– close (16 mm) to the beam interaction point,– best possible heavy flavour tagging; • Fine-granularity calorimeters– particle flow (PFA) calorimetryis an asset,– provides necessary jet energy resolution; • Solenoid magnetic field of 3.5 T– upgradable to 4 T (for the ILC 1 TeV stage); • Almost 4π geometric acceptance– to the benefit of tracking & calorimetry. Basic design parameters (ILD_00): HEPHY Vienna is founding member of the ILD proto-collaboration. ILD is one of two ILC detector concepts “validated” by IDAG in April 2009. Winni Mitaroff: ÖPG-FAKT

  8. The ILD silicon trackers Domain of HEPHY Vienna’s hardware contributions ! Winni Mitaroff: ÖPG-FAKT

  9. ILD Forward Tracking Detector (FTD) Winni Mitaroff: ÖPG-FAKT

  10. Forward track reconstruction in ILD New stand-alone software package ForwardTracking: Stage 1: Cellular Automaton (CA), Stage 2: Kalman Filter (KF), Stage 3: Hopfield Neural Network (HNN). Embedded in ILD’s software framework Marlin. Winni Mitaroff: ÖPG-FAKT

  11. Stage 1: the Cellular Automaton (CA) Fast semi-global track finding method: • Takes all hits into account simultaneously, but situation evolves based on local rules; • Track segments interact with connected ones and are tested for compatibility. Winni Mitaroff: ÖPG-FAKT

  12. Stage 2: the Kalman Filter (KF) • Two main goals: • Track parameter determination, • Chi-squared probability gives feedback aboutthe track quality; • Chi-squared probability cut value = 0.005; • Algorithms called:KalTest+ KalDet + MarlinTrk. Note: an ultimate track fit by a KF + smoother will alsobe performed, after track search, on the final sample ! Winni Mitaroff: ÖPG-FAKT

  13. Stage 3: Hopfield Neural Network (HNN) • Ambiguity resolving:this is the last stage in forward track search; • Tracks sharing hits are incompatible:overlap comes from combinatoricsin reconstruction⇒ ghosts and clones: Winni Mitaroff: ÖPG-FAKT

  14. How does the HNN work ? • Tracks are assigned a quality and an activation state, and they do dynamically interact; • Compatible tracks amplify each other,whereas incompatible ones weaken each other; • In order to prevent oscillation between states, updating is done asynchronously; • A global extremum is searched for – in order to avoid falling into a local one, an annealing scheme is used (by assigning the system a “temperature” being cooled down). Winni Mitaroff: ÖPG-FAKT

  15. Performance: efficiency • ForwardTracking: new forward tracking package, • SiliconTracking: old package (still used in barrel), • TrackSubsetProcessor: combines results of both. Winni Mitaroff: ÖPG-FAKT

  16. Performance: ghost rate • ForwardTracking: new forward tracking package, • SiliconTracking: old package (still used in barrel), • TrackSubsetProcessor: combines results of both. Winni Mitaroff: ÖPG-FAKT

  17. Performance: processing time • ForwardTracking: new forward tracking package, • SiliconTracking: old package (still used in barrel). Background scaled conforming to the LoI with 500 GeV ! Winni Mitaroff: ÖPG-FAKT

  18. Conclusions and Outlook • A new software package for stand-alone track reconstruction in the forward region of ILD has been successfully developed and implemented; • It shows superior performance w.r.t. the old ILD software (originally developed for the barrel); • Our ForwardTracking package is on board for benchmark processing for ILD’s “Detailed Base-line Design” (DBD) report, due by Dec. 2012; • Our package will also be used for a modified ILD detector at the “Compact Linear Collider” (CLIC). Winni Mitaroff: ÖPG-FAKT

  19. Backup Slides Winni Mitaroff: ÖPG-FAKT

  20. Toy detector: true tracks Winni Mitaroff: ÖPG-FAKT

  21. True hits (green) +background hits (red) Winni Mitaroff: ÖPG-FAKT

  22. CA: building segments (“cells”) Winni Mitaroff: ÖPG-FAKT

  23. CA: iteration #1 (redstates) Winni Mitaroff: ÖPG-FAKT

  24. CA: iteration #2 (orange states) Winni Mitaroff: ÖPG-FAKT

  25. CA: iteration #3 (green states) Winni Mitaroff: ÖPG-FAKT

  26. CA: iteration #4 (blue states) Winni Mitaroff: ÖPG-FAKT

  27. CA: after clean-up of bad states Winni Mitaroff: ÖPG-FAKT

  28. KF + HNN: final tracks found Winni Mitaroff: ÖPG-FAKT

  29. Two machine studies: ILC and CLIC The CERN Linear Collider Detector Project: adapting the ILC detector concepts for the higher CLIC energies (CLIC_ILD, CLIC_SiD), and using the software developed by the ILC collaborations for simulation and optimization studies. The decision ILC vs. CLIC will be based on “new physics” results from LHC. If it will be in favour of CLIC, the ILC detector collaborations will move. Winni Mitaroff: ÖPG-FAKT

  30. Detector performance requirementsof ILC / CLIC vs. those of LHC • ○ Inner vertex layer ~ 3 - 6 times closer to IP • ○ Vertex pixel size ~ 30 times smaller • ○ Vertex detector layer ~ 30 times thinner • Impact param resolution: Δd ≤ 5 μm + 10 μm / [ (p/GeV) x sin3/2 θ ] • ○ Material in the tracker ~ 30 times less • ○ Track momentum resolution ~ 10 times better • Momentum resolution: Δp / p2 ≤ 5 x 10-5 / GeV “barrel region”, • Δp / p2 ≤ 3 x 10-5 / GeV “forward region” • ○ Granularity of EM calorimeter ~ 200 times better • Jet energy resolution: ΔE / E ≤ 0.3 /√E • Forward hermeticity down to θ ≥ 5 - 10 mrad Winni Mitaroff: ÖPG-FAKT

  31. Forward region of ILD_00 layout • Very forward region:– 5.00 < ϑ < 11.50: only FTD measuremts. contributing,– Range of FTD 1 (2) starts where that FTD 6 (7) ends. • Intermediate region:– 11.50 < ϑ < 25.50: complex mix of VTX + FTD + TPC,– FTD: only FTD 1 … 3, plus FTD 4 until ϑ < 16.50,– TPC: 10 pad-rows @ 11.50 … 100 pad-rows @ 25.50. • Barrel + FTD 1 only: • – 25.50 < ϑ < 36.70: VTX + FTD 1 + SIT + TPC. • ETD: ignored by track fitting (no more precision) • – 9.80 < ϑ < 36.90: PR link to fwd. ECAL, useful in PFA. ϑ = 900 36.70 25.50 16.50 11.50 10 padrows → 80 50 FTD 1 2 3 4 5 6 7 Pixel disks Double-sided (stereo angle) strip disks Winni Mitaroff: ÖPG-FAKT

  32. Spurrekonstruktion für FTD • Jeder Detektor ist anders • Hintergrund • Paarbildung (Photonen) • Pixels: aufintegrierte Events • Strips: Ghost Hits • Geschwindigkeit • Efficiency und Ghost Rate • Wart- und Lesbarkeit FTD TPC Winni Mitaroff: ÖPG-FAKT

  33. Processors in ILD’s framework “Marlin” Winni Mitaroff: ÖPG-FAKT

  34. For compatibility cut off criteria are needed • Cut offs rely on analysis of true tracks • Efficiency vs. ghost rate & computing time Winni Mitaroff: ÖPG-FAKT

  35. Conways Spiel des Lebens Winni Mitaroff: ÖPG-FAKT

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