Forward Tracking Report of the Vienna iLCsoft Group

1. Forward TrackingReport of the Vienna iLCsoft Group Winfried A. Mitaroff “Discussion document”at the 5th ILD Workshop and SiLC Meeting LAL Orsay / APC Paris VII, May 2011

2. Vienna’s commitment to ILD • MarlinReco’s Track Search and Reconstruction based on wrapped legacy Fortran 77 code (from LEP era). • Urgent need to re-write this from scratch in C++. • HEPHY agreed in fall 2009, as a “significant contribution to ILD”, to provide the new processor for tracking in the forward region (stand-alone track search shared). • Required for processing data for the “Detailed Baseline Design” (DBD), i.e. to be released by spring 2012 ! • Scheduled start in October 2010 delayed until May 2011, due to problems recruiting a diploma/PhD student. • Started with a new student (Robin Glattauer) on 9 May. Mitaroff: Discussion document at ILD#5 and SiLC

3. Forward region (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 Mitaroff: Discussion document at ILD#5 and SiLC

4. Forward tracking sub-tasks • FTD geometry description (done), \ • FTD drivers in Mokka (done), } not by Vienna • FTD digitizations in Marlin (missing). / • FTD stand-alone track search –– shared task(very fwd. and intermediate regions, 50 < ϑ < 25.50);Valencia’s stand-alone silicon track search may be evaluated for FTD. • TPC-supported track search(optional in intermediate region, 11.50 < ϑ < 25.50). • DAF-based final hit associations. • Precision forward track fit. • Region 25.50 < ϑ < 36.70 is “mostly barrel”(VTX, SIT, TPC) with only one FTD 1 ➯ barrel or fwd. task ? Mitaroff: Discussion document at ILD#5 and SiLC

5. Fwd. track search strategies • Stand-alone in FTD: • This is the only possible strategy in the very forward region, • Various algorithms exist – which to chose needs careful study, • For small ϑ, hits from beamstrahlung-induced background may cause further problems (we need a reliable estimate), • Layout for optimized track resolution (e.g. strip orientation and stereo angle) not necessarily optimal for track search. • Combined TPC–FTD: • This may be an optional strategy for the intermediate region: • Inward extrapolation of tracks found by local PR in the TPC,FTD hits tested against and associated to them, • Timing problems hopefully solved by “time stamps”. • Soft hit association: • Hits may be shared among tracks, and the final association relegatedto track reconstruction based on the DAF. Mitaroff: Discussion document at ILD#5 and SiLC

6. Forward track reconstruction • Algorithms used: • Based on the Kalman Filter, with robustification by the adaptive Deterministic Annealing Filter (DAF): • (1) Testing and updating the track hypothesis (hit associations) by identifying and removing “outliers”, and resolving ambiguous associations from the track search, • (2) Performing a precision track fit. • Special features: • Flexible track navigation in the complex intermediate region,coping with inclined or staggered plaquettes of FTD. • Energy loss of electrons modeled by the Gaussian Sum Filter (GSF) ➯ requires extension of the LCIO data model, • Magnetic field distortions by the “anti-DiD” taken into account (small “Billoir corrections” on helices, or Runge-Kutta). Mitaroff: Discussion document at ILD#5 and SiLC

7. Design and implementation • The user API should be common for barrel and forward tracks. • However, the implementation is suggested to be separate and complimentary for the barrel and the forward regions: • Optimal track search algorithms will differ for barrel and fwd., • Internal track representations may differ (e.g. 1/pT vs. 1/P), • Coordinated independence of the two programming teams. • A small MarlinReco control processor for the required top-level steering “barrel vs. fwd. calls”, transparent to the user. • Coordination is enhanced by a common pool of utility classes; however, the skeleton GenFit is preferred over KalTest. • Both implementations will rely on common interfaces, e.g. for • Using available results from a previous track search in TPC, • Persistency by the new LCIO data model, augmented for GSF, • Interfacing the new GEAR geometry toolkit (written by CERN). Mitaroff: Discussion document at ILD#5 and SiLC

8. Sharing of responsibilities Discussions with F. Gaede and A. Ruiz at ILD Meetings in July & Oct. 2010, consent about sharing of tasks for the new ILD tracking: • DESY Hamburg:Overall coordination and all barrel tracking: work has started. • Spain (Santander, Valencia) and HEPHY Vienna:All forward tracking, with the sub-tasks • (1,2) FTD geometry description, drivers in Mokka: Spain, • (3) FTD digitizations: Spain with contributions by Prague, • (4) FTD stand-alone fwd. track search: Spain and Vienna, • (5) TPC-supported fwd. track search: Vienna, • (6,7) DAF-based fits, precision track fit: Vienna. Meanwhile, Paris VII (Aurore et al.) had contributed sub-tasks 1 and 2, and will take care of sub-tasks 3 (with Prague) and 4(with Vienna). Mitaroff: Discussion document at ILD#5 and SiLC

9. iLCsoft manpower @ Vienna • Winni Mitaroff (head, will retire Dec. 2011, unpaid consultant thereafter) • New undergraduate student: • Robin Glattauer:Project work started 9 May on Marlin / MarlinReco,will be continued as a diploma thesis at TU ViennaJuly ‘11 – June ’12 on the new Forward Tracking (supervision byWinni M., backed byRudi F.) • Part-time support expected: • Rudi Frühwirth (senior staff, statistics guru: Kalman, DAF, GSF …) • Manfred Valentan (PhD student, mastermind fastsim tool “LiC Toy”) • Wolfgang Waltenberger (junior staff, mastermind vertex tool RAVE) • Aim at a first version of the new Forward Tracking to be used for the DBD ! • Possibly follow-on study on backgrounds in the forward region ? Mitaroff: Discussion document at ILD#5 and SiLC

10. Vienna’s contract with AIDA“Advanced European Infrastructures for Detectors at Accelerators” • Official start at Kickoff Meeting,16-18 February 2011 at CERN • HEPHY participates in 2 of 9 “Working Packages” (contact: M. Krammer) • WP 2: “Common Software Tools”(coordinators: F. Gaede,P. Mato) • Task 2.2: “Geometry Toolkit for HEP” • Task 2.3: “Reconstruction Toolkits for HEP”(coord.: F. Gaede, DESY) • Sub-task 2.3.a: “Tracking Toolkit”(coordinator: St. Aplin, DESY)* Sub2-task “Barrel Tracking”: DESY, ...* Sub2-task “Forward Tracking”: Santander, Valencia, Vienna • Sub-task 2.3.b: “Alignment” • Sub-task 2.3.c: “Pile-up Events” • Sub-task 2.3.d: “PFA Calorimetry” • Diploma student’s supervisor eligible for 1/3 salary refunding by AIDA • Deliverable: generic toolkit within 38 months (due by end April 2014) Mitaroff: Discussion document at ILD#5 and SiLC

11. ILD vs. AIDA implementation • AIDA sub-task 2.3.a • Deliverable: generic toolkit for Track Reconstruction. • Timescale: February 2011 – April 2014 (38 months). • ILD track reconstruction • Processor in MarlinReco: wrapped legacy Fortran code,used for the 2009 LoI. Urgent need of new C++ code ! • Timescale: now – early 2012, to be used for the DBD. • Pragmatic solution • Coding for ILD may serve as a “pilot implementation”. • Needs clear separation generic vs. detector-dependent. • Experience gained will be used for the AIDA deliverable. Mitaroff: Discussion document at ILD#5 and SiLC

12. Backup Slides Mitaroff: Discussion document at ILD#5 and SiLC

13. Software expertise at Vienna • “Vienna School” of detector-related data analysis • Founded in the late 1970s by Meinhard Regler at HEPHY Vienna. • Contributions to experiments since ~ mid 1980s • LEP-DELPHI, framework DELANA (f77): Local PR of FCA. Forwardtrack fit incl. VFT (Kalman), later merged with barrel for reprocessing. • LHC-CMS, framework CMSSW (C++): Track and vertex reconstruction(Kalman, pioneering DAF, GSF). Offspring: vertex reco toolkit RAVE. • Detector-independent tool LDT (MatLab) for fast simulation and trackreconstruction (Kalman). Used for optimizing ILD and CLIC detectors. • KEKB-Belle II, framework BASF 2 (C++): Track search in SVD. Trackfit in PXD-SVD-CDC (Kalman, DAF, GSF). Both are still in progress. • Dept. for Algorithms and Software Development • Headed by Rudi Frühwirth. A recent publication of general interest:A. Strandlie and R. Frühwirth, Rev.Mod.Phys. 82 (2010) 1419-1458. Mitaroff: Discussion document at ILD#5 and SiLC

14. Contributions to ILD by Vienna • ILD detector optimization: • Evaluation of various tracker layouts, with emphasis on tracking quality in the difficult forward and intermediate regions. • Development of optimization algorithms, and of a detector-independent fast simulation tool (“LiC Detector Toy” = LDT). • Major contributions to the ILD “Letter of Intent”, which was the basis for IDAG’s 2009 approval of this detector concept. • iLCsoft (Software for ILC Detectors): • Development of a detector-independent vertex reconstruction toolkit (RAVE), based on “robust” algorithms developed for CMS. • Development of a new Track Reconstruction in the forward region ofthe ILD detector (a major contribution, work starting now). • SiLC (Silicon for Linear Colliders): • Generic R&D programme to develop low material budget high-precision tracker modules, based on silicon micro-strip technology. • Design and construction of a Si envelope around a large prototype TPC inside a superconducting magnet at a test beam at DESY. Mitaroff: Discussion document at ILD#5 and SiLC

15. What is the “forward region” ? • Very forward region • 50 < ϑ < 11.50:only FTD measurements 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: 9.80 < ϑ < 36.90 • Ignored by track fitting: cannot contribute to precision, • Useful for PFA (pattern recognition link to fwd. ECAL). Mitaroff: Discussion document at ILD#5 and SiLC

16. Forward tracking summary • Forward track search: • Stand-alone in the FTD: careful choice among various algorithms, • Combined TPC – FTD in the intermediate region (“time stamps”), • Soft hit associations ➯ resolved later by the DAF. • Forward track reconstruction: • Algorithms based on the Kalman Filter, with robustification by the adaptive Deterministic Annealing Filter (DAF). • (1) Testing and updating the track hypothesis (hit associations) by identifying and removing “outliers”, and resolving ambiguous associations from the track search, • (2) Performing a precision track fit. • Energy loss of electrons modeled by a Gaussian Sum Filter (GSF), • Magnetic field distortions by the “anti-DiD” to be taken into account. • Usage of a skeleton toolkit (GenFit or KalTest) ? Mitaroff: Discussion document at ILD#5 and SiLC

17. LDT example: forward optimization (M. Valentan: presented at the 8th SiLC Meeting, Santander, Dec. 2008) Mitaroff: Discussion document at ILD#5 and SiLC

18. Track model for the GSF Mitaroff: Discussion document at ILD#5 and SiLC

19. Off topic: RAVE vertexing • Detector-independent vertex recon-struction toolkit: RAVE • Developed 2004–08 by W. Waltenberger (master mind), F. Moser, B. Pflugfelder and H.V. Riedel, • Interfaced to topological vertex search ZvTop, • Standard vertexing for CMS, Belle II (and 4th), • Pilot implementations in ILD’s “Marlin” and SiD’s Java-based “org.lcsim” frameworks exist, but … • The “rival”: LCFIvertex (tools ZvTop, ZvRes, ZvKin, ZvMst) • Developed by D.J. Jackson, S. Hillert, B. Jeffery et al., mostly at Oxford and RAL until 2009; then support taken by Japan (Tohoku, KEK, Tokyo), • De-facto standard vertexing for ILD and SiD. • New effort to reconcile RAVE with LCFIvertex: • Comparison study with ZvTop/ZvRes: recent meeting in Bonn 12 May 2011(W. Waltenberger,S. Hillert et al.). • W. Waltenberger:RAVE – a detector-independent toolkit to reconstruct vertices,IEEE Transactions on Nuclear Science, 2011, DOI 10.1109/TNS.2011.2119492 (08.03.2011). Mitaroff: Discussion document at ILD#5 and SiLC