1 / 12

CA+KF Track Reconstruction in the STS

CA+KF Track Reconstruction in the STS. S. Gorbunov and I. Kisel GSI/KIP/LIT. CBM Collaboration Meeting Dresden, September 26, 2007. CBM Note on SIMDized Kalman Filter Track Fit. Different CPU architectures.

nyla
Download Presentation

CA+KF Track Reconstruction in the STS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CA+KF Track Reconstructionin the STS S. Gorbunov and I. Kisel GSI/KIP/LIT CBM Collaboration Meeting Dresden, September 26, 2007

  2. CBM Note on SIMDized Kalman Filter Track Fit Different CPU architectures The Kalman filter based track fit works with single precision floating point variables, and we are now not far from implementing it in integers in order to port it later to FPGA. Implemented: in CbmL1CATracker Ivan Kisel, KIP, Uni-Heidelberg

  3. Cellular Automaton Pseudocode Create tracklets Collect tracks 1 2 Ivan Kisel, KIP, Uni-Heidelberg

  4. Reconstruction Time vs. Number of MC Tracks (0) fast quasi-primary tracks (1) all quasi-primary tracks (2) all tracks Ivan Kisel, KIP, Uni-Heidelberg

  5. Structure and Data • A standalone L1Algo module • About 300 kB per central event cbmroot/L1 L1Tracks L1Event (L1Strips, L1Hits) L1Geometry L1Algo Input: Strips: floatvStripValues[NStrips]; // strip coordinates (32b) unsigned charvStripFlags [NStrips]; // strip iStation (6b) + used (1b) + used_by_dublets (1b) Hits: struct L1StsHit { unsigned short int f, b; // front (16b) and back (16b) strip indices }; L1StsHitvHits[NHits]; unsigned short intvRecoHits [NRecoHits]; // hit index (16b) unsigned charvRecoTracks [NRecoTracks]; // N hits on track (8b) class L1Triplet{ unsigned short intw0; // left hit (16b) unsigned short intw1; // first neighbour (16b) or middle hit (16b) unsigned short intw2; // N neighbours (16b) or right hit (16b) unsigned charb0; // chi2 (5b) + level (3b) unsigned charb1; // qp (8b) unsigned charb2; // qp error (8b) } Output: Internal: Ivan Kisel, KIP, Uni-Heidelberg

  6. Event Display Ivan Kisel, KIP, Uni-Heidelberg

  7. CA Track Finder Efficiency Standard geometry: 2M2P4S Central events MBias events Reconstructed + (Damaged + Good) Ivan Kisel, KIP, Uni-Heidelberg

  8. Low Momentum Tracks 1. In general, efficiency calculation is based on similarity between parameters of generated and reconstructed tracks. 2. The simplest efficiency calculation is based on association of hits used for track fitting. 3. In the region of low momentum tracks it can be based on association of hits within the track road because of large multiple scattering and high hit density. Therefore, ghost in (2) can here contribute to (1). Central events Ivan Kisel, KIP, Uni-Heidelberg

  9. Detector Inefficiency • Tracking is gathering of 1/2D measurements into 5D tracks, here combinatorics • Therefore, tracking is split into two parts: local (1) and global (2) • In the local part a gap between 1/2D and 5D is filled with triplets • If there is no triplet in the local step, no track in the global step • Therefore, short tracks are weak against detector inefficiency • Tracks interesting for physics are usually long (long vs. short tracks) • Specialized extra tracking step (usually indicates weakness of the detector) • Increase acceptance (<- Rin, Rout ->) keeping Nch constant (longer or chained strips) • Double stations – 4x-, 3x-, 2x-strip space points (no inefficiency, no dead zones) Ivan Kisel, KIP, Uni-Heidelberg

  10. CA Track Finder Efficiency Standard geometry: 2M2P4S Central events MBias events Reconstructed + (Damaged + Good) Detector efficiency (MC points) 98% Ivan Kisel, KIP, Uni-Heidelberg

  11. CBM Note on Reconstruction of Decayed Particles x, y, z, px, py, pz, E, m, L, ct K- p+ D0 In addition to vertices, which are now production and decay points, all physical parameters of decayed particles together with the corresponding errors are provided by the package. Implemented: in CBM as CbmKFParticle in ALICE as AliKFParticle Ivan Kisel, KIP, Uni-Heidelberg

  12. Summary and Plans • SIMDized CA and KF algorithms are released • Low momentum tracks down to 100 MeV/c are found by default • CA track finder works with inefficient detectors • Need direct access to strips (fixed geometry at the level of modules) • Further analysis of robustness of the CA track finder Ivan Kisel, KIP, Uni-Heidelberg

More Related