Track strategy tuning

The LCSim Java package used for track reconstruction in the FPaDSim software chain relies on a list of “tracking strategies,” which is a list of tracking layer collections for seeding, confirming, and extending tracks. These collections must be optimized for a particular geometry configuration and can be tuned for minimum number of hits, max chi^2, etc. In order to optimize the strategies list, a representative data set must be simulated, containing a significant number of tracks that span the phase space and particle species to be tracked. This then serves as an input to the strategy list builder built into the LCSim package. Additionally, a set of configuration files specify the requirements of the track fit, and the parameters used for the seeding algorithm.

The ingredients for building the strategy list are…

• traningSample.slcio - An LCIO file filled with simulated particles
• strategyBuilder.xml - A configuration file for building the strategy list
• prototypeStrategy.xml - A prototype tracking strategy
• layerWeights.xml - A file for specifying weights for seed layers

Generated in FPaDSim with SLIC, this file serves as a broad representation of tracks to be fitted. A reasonable approach is to fill this file with various species of particles, each flatly distributed in pseudorapidity and an appropriate range of transverse momenta.

An example file is found below.

<lcsim xmlns:lcsim="http://www.lcsim.org/schemas/lcsim/1.0"
    xmlns:xs="http://www.w3.org/2001/XMLSchema-instance"
    xs:noNamespaceSchemaLocation="http://www.lcsim.org/schemas/lcsim/1.0/lcsim.xsd">
  <inputFiles>
    <file>${trainingSampleFile}</file>
  </inputFiles>
  <control>
    <numberOfEvents>-1</numberOfEvents>
    <verbose>false</verbose>
    <printDriverStatistics>true</printDriverStatistics>
    <printDriversDetailed>true</printDriversDetailed>
  </control>
  <execute>
    <driver name="StrategyBuilder"></driver>
  </execute>
  <drivers>
    <driver name="StrategyBuilder" type="org.lcsim.recon.tracking.seedtracker.strategybuilder.StrategyBuilder">
      <output type="String">${outputStrategyFile}</output>
      <symmetrize type="boolean">true</symmetrize>
      <layerWeight type="String">${layerWeightsFile}</layerWeight>
      <strategyPrototype type="String">${prototypeStrategyFile}</strategyPrototype>
      <minLayers type="int">5</minLayers>
      <numConfirmLayers type="int">1</numConfirmLayers>
      <numSeedLayers type="int">3</numSeedLayers>
      <verbose type="boolean">true</verbose>
    </driver>
  </drivers>
</lcsim>