GeneratedParticleInfo.h

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/**
 * @file   lardataobj/Simulation/GeneratedParticleInfo.h
 * @brief  Contains data associated to particles from detector simulation.
 * @author Gianluca Petrillo (petrillo@fnal.gov)
 * @date   January 10, 2018
 *
 */

#ifndef LARDATAOBJ_SIMULATION_GENERATEDPARTICLEINFO_H
#define LARDATAOBJ_SIMULATION_GENERATEDPARTICLEINFO_H

// LArSoft libraries
#include "nusimdata/SimulationBase/simb.h" // sim::GeneratedParticleIndex_t, ...


namespace sim {

  /**
   * @brief Contains information about a generated particle.
   *
   * This information is designed to be added as metadata to an association
   * between a `simb::MCParticle` produced by the simulation of particle
   * propagation through the detector (e.g. `LArG4`) with the generator truth
   * record that particle derives from:
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
   * art::Assns<simb::MCParticle, simb::MCTruth, sim::GeneratedParticleInfo>
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   * The associated `simb::MCParticle` is expected to be the generated particle
   * of the generator truth record, as processed by the simulation.
   * The provided information is currently:
   * * index of the generated particle within the generator record; the particle
   *   itself can be obtained as:
   *   @code{.cpp}
   *   mctruthPtr->GetParticle(genParticleInfo.generatedParticleIndex());
   *   @endcode
   *
   */
  class GeneratedParticleInfo {

      public:

    //--- BEGIN Generated particle index ---------------------------------------
    /// @{
    /// @name Generated particle index

    /// Type of particle index in the generator truth record (`simb::MCTruth`).
    using GeneratedParticleIndex_t = simb::GeneratedParticleIndex_t;

    /// Constant representing the absence of generator truth information.
    static constexpr GeneratedParticleIndex_t NoGeneratedParticleIndex
      = simb::NoGeneratedParticleIndex;

    /**
     * @brief  Returns the generated particle index.
     * @return generated particle index (`NoGeneratedParticleIndex` if none)
     */
    GeneratedParticleIndex_t generatedParticleIndex() const
      { return fGeneratedParticleIndex; }

    /// Returns whether the specified one is an acceptable generator index.
    bool hasGeneratedParticleIndex() const
      { return simb::isGeneratedParticleIndex(fGeneratedParticleIndex); }

    /// @}
    //--- END Generated particle index -----------------------------------------


    //--- BEGIN Constructors ---------------------------------------------------
    /// Default constructor (for ROOT I/O only).
    GeneratedParticleInfo() = default;

    /**
     * @brief Constructor: assigns all the values.
     * @param index generated particle index (`NoGeneratedParticleIndex` if none)
     */
    GeneratedParticleInfo(GeneratedParticleIndex_t index)
      : fGeneratedParticleIndex(index)
      {}
    //--- END Constructors ---------------------------------------------------


      private:

    /// Index of the generated particle in its `simb::MCTruth` record.
    GeneratedParticleIndex_t fGeneratedParticleIndex = NoGeneratedParticleIndex;

  }; // class GeneratedParticleInfo



} // namespace sim

#endif // LARDATAOBJ_SIMULATION_GENERATEDPARTICLEINFO_H