CHEP 2000 Padova ITALY 07 11 February 2000

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Implementation of an Object Oriented Track Reconstruction Model into Multiple LHC Experiments

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Outline • Overview of LHC, CMS and Atlas • Review of the OO track reconstruction model • Implementation of the OO model into CMS ORCA (Object-oriented Reconstruction for CMS Analysis) • Implementation of the OO model into Atlas LVL-2 trigger reference SW and performance • Experience and lessons learned • Summary and prospects CMS & Atlas OO Tracker Model Implementation S. Qian 2

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS & Atlas LHC OO Tracker Model Implementation S. Qian 3

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS and ATLAS CMS & Atlas OO Tracker Model Implementation S. Qian 4

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Trackers of CMS and Atlas CMS ATLAS CMS & Atlas OO Tracker Model Implementation S. Qian 5

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 OO Tracker Model (I) Atlas • Brief history -- Initial analysis and design by Irwin GAINES and Sijin QIAN (3/1995) -- Started C++ coding based on a Fortran Kalman filter tracking package (9/95) -- The model re-design by using STL (2/1996) -- Accomplished the tracking finding and fitting (autumn 1996) -- Ported to Windows NT (the beginning of 1997) ** a contribution published in proceedings of CHEP’ 97, Berlin, Germany (4/1997) -- A partial re-design to form an abstract Track_builder class (summer 1997) -- Tested in Atlas environment (end of 1997) and started LVL-2 implem. (9/98) ** a presentation by Irwin at CHEP’ 98, Chicago, U. S. A. (9/1998) -- Produced the pure C++ version (3/1999) ** a presentation by Sijin at AIHENP’ 99, Crete, Greece (4/1999) -- Released to Atlas LVL-2 reference SW (5/1999) and Ctrig (8/1999) -- Preliminarily integrated into ORCA (8 -9/1999) CMS & Atlas OO Tracker Model Implementation S. Qian 6

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas OO Tracker Model (II) • Main ingredients of the OO model: – Problem statement ==> class diagram – Function statement ==> object diagrams and message trace diagrams • Main features of the model: – Use well known HEP concepts for classes – Extensive use of Standard Template Library (STL), in both model design and C++ coding – Initially successful re-use of FORTRAN legacy code (for Kalman filtering method) in the member functions of various classes; later converted them to C++ in a straightforward manner; now pure C++ – Flexible enough to be re-used in multiple HEP experiments (only implementation of layer class is different) CMS & Atlas OO Tracker Model Implementation S. Qian 7

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas The latest version of class diagram CMS & Atlas OO Tracker Model Implementation S. Qian 8

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Object Diagrams Atlas First scenario CMS & Atlas OO Tracker Model Implementation Second scenario S. Qian 9

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS Implementation • Uses first scenario (internal hit triplets as seeds) • Conceptual structure of “mytest. cpp” in the ORCA example directory – Rec. Hit objects (in ORCA) are converted to “hit” object of the OO model. – Layer objects of OO model are instantiated with hard-wired code at this stage, can be done from ORCA tracker geometry in future. – All classes in the OO KF tracking model are brought in straightforwardly without any major change. • Examples of reconstructed tracks from the output log file CMS & Atlas OO Tracker Model Implementation S. Qian 10

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Conceptual structure of “mytest. cxx” in ORCA example directory CMS & Atlas OO Tracker Model Implementation S. Qian 11

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS & Atlas OO Tracker Model Implementation S. Qian 12

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS & Atlas OO Tracker Model Implementation S. Qian 13

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas CMS & Atlas A Reconstructed Event OO Tracker Model Implementation S. Qian 14

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Implementation (I) • LVL-2 trigger requirement (O(10 ms) time slot) ==> execution time is a factor of concern. – use 2 nd scenario (outside seeds) – do reconstruction in Region of Interest (Ro. I) instead of in full f-h range • Frameworks – LVL-2 Reference Software system (OO designed, input ASCII data) – Ctrig (input from ASCII files, produce ntuples, etc. ) • Seed modes: (1) TRT guided (inward pattern recognition) (2) pixel guided (outward pattern recognition) • Tracking corrections: (1) Multiple scattering (yes); (2) Energy loss (yes for electrons); (3) Non-uniform B field (in near future). CMS & Atlas OO Tracker Model Implementation S. Qian 15

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Energy Loss Correction D (1/Pt) distribution (1/Ge. V) 1 Ge. V electrons CMS & Atlas 5 Ge. V electrons OO Tracker Model Implementation 20 Ge. V electrons S. Qian 16

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Implementation (II) • Performance: – Execution speed (on 300 MHz Pentium II, under Linux) Single m (no pile-up) B-physics (at low luminosity) – – – TRT seeded <1. 3> ms/event <725> ms/event (<262> seeds) Pixel seeded -<320> ms/event (<122> seeds) Memory usage is in O(10 MB), depends on data volume Efficiencies (single track events, B-physics events) Resolutions (momentum, impact parameter, etc. ) B-physics study in the channel B --> pp Many more results are at http: //www-wisconsin. cern. ch/~sijinat/lvl 2/res. html http: //www-wisconsin. cern. ch/~atsaul/results/sctkalman/ CMS & Atlas OO Tracker Model Implementation S. Qian 17

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Efficiencies for m and e muons electrons – CMS & Atlas OO Tracker Model Implementation S. Qian 18

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Efficiencies for B-physics (1) Atlas e vs. Pt e for e from B 0 --> J/f e vs. h – CMS & Atlas OO Tracker Model Implementation S. Qian 19

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Efficiencies for B-physics (2) Atlas e vs. Pt e for e from B 0 --> pp e vs. h – CMS & Atlas OO Tracker Model Implementation S. Qian 20

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas 1/Pt Resolutions 20 Ge. V m (tops: barrel; bottoms: endcap) D 0 – CMS & Atlas OO Tracker Model Implementation S. Qian 21

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas B-physics mass reconstruction Reconstruction of B --> pp mass hypothesis in ATLAS Level-2 trigger using the Kalman filtering method CMS & Atlas OO Tracker Model Implementation S. Qian 22

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Lessons Learned • C++’s new features (for previous Fortran programmers) now can be handled by some powerful debugging tools, e. g. – “INSURE++” to detect the memory leaks – “DDD” graphic debugger to detect the pointer bugs • Integration of an OO model into a general OO environment of whole experiment needs a stable framework with a stable interface. As soon as all functionality of I/O objects needed by the model are available, the integration is straightforward. CMS & Atlas OO Tracker Model Implementation S. Qian 23

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Conclusions • OO makes it easier to do cooperative development among widely separated collaborators (promotes truly modular designs) • OO makes re-use easier: the implementation of this OO model into two LHC experiments demonstrates: -- the implementation structure is very similar for different experiments -- the experience in code development can be shared among different experiments immediately CMS & Atlas OO Tracker Model Implementation S. Qian 24

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Summary and Prospects • We are moving towards a realistic OO track reconstruction model for HEP experiments – the memory usage of this OO model is moderate – the track finding efficiency is satisfactory – the execution speed is approaching the LVL-2 trigger requirement • It can be used in different experiments with only minor modifications CMS & Atlas OO Tracker Model Implementation S. Qian 25

CHEP‘ 2000 Padova, ITALY 07 -11 February 2000 Atlas Ongoing and Future Work • CMS: -- Investigate more efficient I/O functions -- Use finalized CMS detector and track classes -- Overhaul the package with CMS coding rules • Atlas: -- Implement the non-uniform B-field correction -- Optimize the performance by investigating new seeding methods and by exploring new reconstruction strategies CMS & Atlas OO Tracker Model Implementation S. Qian 26