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Neural ITS stand-alone tracking as a possible HLT algorithm

Neural ITS stand-alone tracking as a possible HLT algorithm. Roberto Barbera and Alberto Pulvirenti ALICE Off-line Week – CERN, June 10-13, 2003. Outlook. Why ? How ? Some results and timing tests. Why ?. ITS stand-alone tracking: “ high-rate acquisition ” phase:

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Neural ITS stand-alone tracking as a possible HLT algorithm

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  1. Neural ITS stand-alone tracking as a possible HLT algorithm Roberto Barbera and Alberto Pulvirenti ALICE Off-line Week – CERN, June 10-13, 2003

  2. Outlook • Why ? • How ? • Some results and timing tests

  3. Why ? ITS stand-alone tracking: • “high-rate acquisition” phase: • HOW: only the fast ALICE detectors turned ON (ITS, Muon-Arm, TRD) • REQUIREMENT: good performance for high transv. momentum particles ( pt >1 GeV/c )

  4. How (Hopfield network with MFT exts.) ? • ITS recpoints are read and loaded in memory

  5. How (Hopfield network with MFT exts.) ? • ITS recpoints are read and loaded in memory • Neurons (oriented segments connecting two recpoints) are created according with some criteria

  6. How (Hopfield network with MFT exts.) ? • ITS recpoints are read and loaded in memory • Neurons (oriented segments connecting two recpoints) are created according with some criteria • After the network stabilization, wrong neurons are “switched off” and only correct sequences stay alive.

  7. Cuts Criteria used to choose which point pairs have to be connected into a “neuron”: • Points on adjacent layers. • Cut on the polar angle difference (q) • Cut on the curvature of the circle passing through the estimated primary vertex and the two points of the pair • “Helix matching cut” …where a is the length of the circle arc going from the vertex projection in the xy plane and each point of the pair.

  8. Pattern recognition workflow “Step by step” procedure: (tracking – tracks saving – used recpoints removal) • Increasing curvature cuts • Azimuthal sectioning of the ITS Potential problem: edge effects Negligeable for high transverse momentum tracks

  9. Ingredients of simulations • Parameterized HIJING in 0 <  < 180 for three multiplicities: • “full” multiplicity (84210 primaries) • “half” multiplicity (42105 primaries = 84210 / 2) • “quarter” multiplicity (21053 primaries = 84210 / 4) • B = 0.2 T and B = 0.4 T and primary vertex in (0, 0, 0) • Full slow reconstruction in ITS and TPC • Evaluation criteria: • “Good” track at least 5 correct points • Otherwise it is labeled as “fake” • “Findable” track: generated track containing at least 5 ITS recpoints • “Efficiency” = # “good” / # “findables”

  10. Results Particles with transverse momentum > 1 GeV/c B= 0.2 T, 20 ITS sectors More results on Thursday !

  11. Timing (FULL event, CPU seconds) On a single PIII @ 1 GHz with 1 GB RAM

  12. Timing (HALF event, CPU seconds) On a single PIII @ 1 GHz with 1 GB RAM

  13. References • A. Badalàet al., NIM A 502 (2003) 503 • 2) A. Badalàet al., ALICE Note 2002-12

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