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ILC.ClusteringAlgorithmr1.1 - 02 Feb 2009 - 16:43 - Main.iglesiastopic end

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Clustering Algorithms

The processor performs clustering of calorimeter hits without using information about reconstructed tracks. The dependence of the clustering procedure on the detector geometry is minimised. Only the follwoing quanteties are used:

  • radius of the ECAL barrel
  • n-fold symmetry of barrel (n = 8 for TESLA)
  • offset of the barrel stave w.r.t. the x-axis (0 for TESLA detector)
  • coordinate of front face of ECAL endcaps
These parameters are taken from the Gear XML file.

TrackwiseClustering Processor

Processor performs clustering of calorimeter hits. No information on reconstructed tracks is used in the clustering algorithm implemented in the Processor.

Processor requires ECAL and HCAL CalorimeterHit? Collections. These are specified with Processor Parameters ECALCollections and HcalCollections?. TrackwiseClustering? produces collection of Clusters

The name of the collection is specified with Processor Parameter ClusterCollection?.

The dependence of clustering procedure on the detector geometry is minimized. Processor needs the following calorimeter geometry parameters :

  • radius of ECAL barrel
  • n-fold symmetry of barrel
  • phi offset of the barrel stave w.r.t.
  • x-axis (0 for TESLA detector)
  • +/- z coordinate of front face of ECAL endcaps
All these parameters are passed to processor via GEAR XML file parameters : DistanceForDirection?, DistanceToTrackSeed?, DistanceTrackBack?, StepTrackBack?, ResolutionParameter?, DistanceMergeForward?, NToDefineSP?, NScanToMergeForward?, TypeOfGenericDistance?, MinimalHitsInCluster?, MaximalHitsToMerge?, UseTracking?, DoMerging?, ResolutionToMerge?, WeightForResolution?, WeightForDistance?.

The meaning of these parameters as well as the overall clustering procedure are described in

Please note, that the parameters steering clustering are optimised for the TESLA detector on hadronic events at Z pole (sqrts=91.2 GeV?). Printout of information on reconstructed clusters is activated if processor parameter DisplayClusterInfo? is set to 1.

-- Main.iglesias - 02 Feb 2009
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