1. 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

2. 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-FAKT21 Sept. 2012

3. Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 Collisions at the TeV scale 3

4. Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 Cross sections at the TeV scale 4 p e – e +

5. Winni Mitaroff: ÖPG-FAKT LHCILC e – e +  Z H Z  e – e +, H  b b … Example: simulated Higgs event – 21 Sept. 20125

6. Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 The International Linear Collider (ILC) – 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 ≈ 2×10 34 cm -2 s -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: Z 0 factory (“GigaZ”), e – e –, e – γ, γγ (“photon collider”). 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. Beam crossing angle 14 mrad; Only 1 experimental zone with 2 detectors operated in “push/pull”. 6

7. Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 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) calorimetry is 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): 7 HEPHY Vienna is founding member of the ILD proto-collaboration. ILD is one of two ILC detector concepts “validated” by IDAG in April 2009.

8. Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 The ILD silicon trackers 8 Domain of HEPHY Vienna’s hardware contributions !

9. Winni Mitaroff: ÖPG-FAKT ILD Forward Tracking Detector (FTD) 21 Sept. 20129

10. Winni Mitaroff: ÖPG-FAKT Forward track reconstruction in ILD 21 Sept. 201210 Stage 1: Cellular Automaton (CA), Stage 2: Kalman Filter (KF), Stage 3: Hopfield Neural Network (HNN). Embedded in ILD’s software framework Marlin. New stand-alone software package ForwardTracking :

11. 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. Stage 1: the Cellular Automaton (CA) 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT11

12. Stage 2: the Kalman Filter (KF) 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT12 Two main goals: Track parameter determination, Chi-squared probability gives feedback about the track quality; Chi-squared probability cut value = 0.005; Algorithms called: KalTest + KalDet + MarlinTrk. Note: an ultimate track fit by a KF + smoother will also be performed, after track search, on the final sample !

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 combinatorics in reconstruction ⇒ ghosts and clones: 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT13

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). 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT14

15. ForwardTracking : new forward tracking package, SiliconTracking : old package (still used in barrel), TrackSubsetProcessor : combines results of both. Performance: efficiency 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT15

16. ForwardTracking : new forward tracking package, SiliconTracking : old package (still used in barrel), TrackSubsetProcessor : combines results of both. Performance: ghost rate 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT16

17. ForwardTracking : new forward tracking package, SiliconTracking : old package (still used in barrel). Performance: processing time 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT17 Background scaled conforming to the LoI with 500 GeV !

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). 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT18

19. Backup Slides 19Winni Mitaroff: ÖPG-FAKT21 Sept. 2012

20. Winni Mitaroff: ÖPG-FAKT Toy detector: true tracks 21 Sept. 201220

21. True hits (green) + background hits (red) 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT21

22. CA: building segments (“cells”) 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT22

23. Winni Mitaroff: ÖPG-FAKT CA: iteration #1 (red states) 21 Sept. 201223

24. Winni Mitaroff: ÖPG-FAKT CA: iteration #2 (orange states) 21 Sept. 201224

25. Winni Mitaroff: ÖPG-FAKT CA: iteration #3 (green states) 21 Sept. 201225

26. Winni Mitaroff: ÖPG-FAKT CA: iteration #4 (blue states) 21 Sept. 201226

27. CA: after clean-up of bad states 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT27

28. KF + HNN: final tracks found 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT28

29. Two machine studies: ILC and CLIC 29Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 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.

30. Detector performance requirements of ILC / CLIC vs. those of LHC 30Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 ○ 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 sin 3/2 θ ] ○ Material in the tracker ~ 30 times less ○ Track momentum resolution ~ 10 times better Momentum resolution: Δp / p 2 ≤ 5 x 10 -5 / GeV “barrel region”, Δp / p 2 ≤ 3 x 10 -5 / GeV “forward region” ○ Granularity of EM calorimeter ~ 200 times better Jet energy resolution: ΔE / E ≤ 0.3 /√E o Forward hermeticity down to θ ≥ 5 - 10 mrad

31. Forward region of ILD_00 layout Winni Mitaroff: ÖPG-FAKT21 Sept. 2012 ϑ = 90 0 36.7 0 25.5 0 16.5 0 11.5 0 8080 5050 10 padrows → FTD 1234567 Very forward region: – 5.0 0 < ϑ < 11.5 0 : only FTD measuremts. contributing, – Range of FTD 1 (2) starts where that FTD 6 (7) ends. Intermediate region: – 11.5 0 < ϑ < 25.5 0 : complex mix of VTX + FTD + TPC, – FTD: only FTD 1 … 3, plus FTD 4 until ϑ < 16.5 0, – TPC: 10 pad-rows @ 11.5 0 … 100 pad-rows @ 25.5 0. Barrel + FTD 1 only: – 25.5 0 < ϑ < 36.7 0 : VTX + FTD 1 + SIT + TPC. ETD: ignored by track fitting (no more precision) – 9.8 0 < ϑ < 36.9 0 : PR link to fwd. ECAL, useful in PFA. Pixel disksDouble-sided (stereo angle) strip disks 31

32. Winni Mitaroff: ÖPG-FAKT Spurrekonstruktion für FTD Jeder Detektor ist anders Hintergrund Paarbildung (Photonen) Pixels: aufintegrierte Events Strips: Ghost Hits Geschwindigkeit Efficiency und Ghost Rate Wart- und Lesbarkeit TPC FTD 21 Sept. 201232

33. Winni Mitaroff: ÖPG-FAKT Processors in ILD’s framework “Marlin” 21 Sept. 201233

34. For compatibility cut off criteria are needed Cut offs rely on analysis of true tracks Efficiency vs. ghost rate & computing time 21 Sept. 2012Winni Mitaroff: ÖPG-FAKT34

35. Winni Mitaroff: ÖPG-FAKT Conways Spiel des Lebens 21 Sept. 201235