Forward Tracking Plans by the Vienna iLCsoft Group

Winfried A. MitaroffAIDA Kick-off Meeting WP2

16 - 18 February 2011

Expertise at HEPHY 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. Forward

track 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.

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Sub-tasks of Work Package 2“Common Software Tools”

(Coordinators: Frank Gaede and Pere Mato)

• Task 2.2: “Geometry Toolkit for HEP”• Task 2.3: “Reconstruction Toolkits for HEP”

(Coordinator: Frank Gaede, DESY)

– Sub-task 2.3.a: “Tracking Toolkit” (Coordinator: Steven Aplin, DESY) * “Barrel Tracking”: DESY, ... * “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”

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Example of a forward region

AIDA Kick-off Meeting WP216 - 18 Feb. 2011

ϑ = 900

36.70

25.50

16.50

11.50

80

50

10 padrows →

FTD 1 2 3 4 5 6 7

The ILD_00 detector forward layout:Very forward region: “forward task”– 5.00 < ϑ < 11.50: only FTD measuremts. contributing,– Range of FTD 1 (2) starts where that FTD 6 (7) ends.Intermediate region: “forward task”– 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: “barrel” or “fwd.” ?– 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.

Pixel disks Double-sided (stereo angle) strip disks

4

Pilot implementation for ILD

• AIDA sub-task 2.3.a– Deliverable: generic toolkit for Track Reconstruction.

– Timescale: spring 2011 – spring 2015 (4 years).

• 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”.

– Experience gained will be used for the AIDA deliverable.

• Next slides: ruminations on the ILD Fwd. Tracking.

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Forward tracking sub3-tasks

1. FTD geometry description,

2. FTD drivers in Mokka,

3. FTD digitizations in Marlin,

4. FTD stand-alone track search(very fwd. and intermediate regions, 50 < ϑ < 25.50),

5. TPC-supported track search(optional in intermediate region, 11.50 < ϑ < 25.50),

6. DAF-based final hit associations,

7. Precision forward track fit.

8. Region 25.50 < ϑ < 36.70 is “mostly barrel” (VTX, SIT, TPC) with only one FTD 1 barrel or fwd. task ?➯

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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 relegated

to track reconstruction based on the DAF.

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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 propagation in the complex intermediate region,– 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).

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Open questions of the design• The user API should be common for barrel and forward tracks.• However, the implementation is suggested to be separate and

complementary 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 skeleton toolkit (GenFitor KalTest), and a pool of utility classes and libraries.

• 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 to the new GEAR geometry toolkit (A. Münnich, CERN).

• Clear separation of generic vs. detector-dependent functionality.16 - 18 Feb. 2011 AIDA Kick-off Meeting WP2 9

Sharing of responsibilities

Discussions at the ILD Software WS (DESY, July ‘10) and thereafter, 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 sub3-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.

Active work expected to start after this Meeting (April ‘11 ?).

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Manpower & funding in Vienna

• Commitment:– Expect a PhD student in his/her first year, to work full-time on

WP2 sub3-tasks 4–7 from spring 2011 for 1+ year;– Follow-up study of background radiation in the forward region,

starting in spring 2012 (overlap with WP9.4 work);– Supervision by Winni M., backed by Rudi Frühwirth;– Work for WP9.4 from mid 2012 onwards (Thomas Bergauer).

• AIDA Proposal:– Rely on 1/3 refunding for 3+ student-years, and travelling costs.

• Budget crisis:– Complementary 2/3 funding by the Austrian Academy of Sci.

(official AIDA partner) is in danger due to severe budget cuts !– Fallback solution if funding fails ? Who could take over ?

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Thank you !