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PC Cluster Reconstruction Algorithm

PC Cluster Reconstruction Algorithm. Paul B. Nilsson Div. of Cosmic and Subatomic Physics, Lund University PHENIX Computing Meeting 4/3/98. Terminology. Pixel : the smallest building block in the printed structure. Pad : the copper electrode build up of 9 pixels.

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PC Cluster Reconstruction Algorithm

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  1. PC Cluster Reconstruction Algorithm Paul B. Nilsson Div. of Cosmic and Subatomic Physics, Lund University PHENIX Computing Meeting 4/3/98

  2. Terminology Pixel: the smallest building block in the printed structure. Pad: the copper electrode build up of 9 pixels. Cell: the square defined by the coincidence of 3 adjacent pads, i.e. a triplet of pixels centered behind a wire. Cluster: a bunch of fired cells.

  3. Outline of the algorithm... S T A R T PCPIX_FIND_CLUSTER PCPIX_NR_OF_PARTICLES Cellx[] Cellz[] = 2 particles ? Yes S T O P No Are there more clusters? Fill STAF tables PCPIX_CALCULATE_POSITION PCPIX_SPLIT_CLUSTER

  4. Present status... • Bug 1: GEANT hit - reconstructed hit = dr, dz = ± 0.4 cm, dx = ± 4 cm for a large HIJING file • Bug 2: The reconstruction of fired cells from fired pads is wrong! Whole clusters are missing. A replacement function has been written, smaller than the original and easier to read. mPadSlowSim needs to be modified. This will be done in the next couple of weeks... • Current settings of cluster size parameters are too large for current HIJING files. Results in an overestimate of the number of particles. HIJING file with between 200-250 particles were reconstructed as 271 particles. Fine tuning will fix this! • “Optimal” data in Lund is reconstructed with an efficiency VERY close to 100% (see pictures at http://www.kosufy.lu.se/staff/paul/cluster.html)

  5. What remains to be done? • Bug fixes! • Fine tuning of the cluster size parameters. • Reconstruction efficiency studies with HIJING events. • 2-track resolution. • Ghosts. • Event display. • 1-particle clusters (look at peripheral events in real data to make “final” adjustments to the size parameters).

  6. Section of a PC sector Fired cell Reconstructed hit Cell Traversing particle

  7. Summary • Algorithm is fully implemented in STAF • Performs very well in design environment • Algorithm is highly dynamical - easy to modify • Evaluation of performance is close at hand

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