TextFileGen_module.cc

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/**
 * @file TextFileGen_module.cc
 * @brief Producer generating Monte Carlo truth record in LArSoft format from a text file
 * @date Mon Apr  8 09:20:02 2013
 * @author Brian Rebel
 */
/**
 * @class evgen::TextFileGen
 *
 *  This module assumes that the input file has the hepevt format for
 *  each event to be simulated.  See
 *
 *  http://cepa.fnal.gov/psm/simulation/mcgen/lund/pythia_manual/pythia6.3/pythia6301/node39.html
 *
 *  for details on the format.  In brief each event contains at least two
 *  lines.  The first line contains two entries, the event number (which is
 *  ignored in ART/LArSoft) and the number of particles in the event.  Each
 *  following line containes 15 entries to describe each particle.  The entries
 *  are:
 *
 *  1.  status code (should be set to 1 for any particle to be tracked, others
 *      won't be tracked)
 *  2.  the pdg code for the particle
 *  3.  the entry of the first mother for this particle in the event,
 *      0 means no mother
 *  4.  the entry of the second mother for this particle in the event,
 *      0 means no mother
 *  5. the entry of the first daughter for this particle in the event,
 *      0 means no daughter
 *  6. the entry of the second daughter for this particle in the event,
 *      0 means no daughter
 *  7. x component of the particle momentum
 *  8. y component of the particle momentum
 *  9. z component of the particle momentum
 *  10. energy of the particle
 *  11. mass of the particle
 *  12. x position of the particle initial position
 *  13. y position of the particle initial position
 *  14. z position of the particle initial position
 *  15. time of the particle production
 *
 *  For example, if you want to simulate a single muon with a 5 GeV energy
 *  moving only in the z direction, the entry would be
 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *  0 1
 *  1 13 0 0 0 0 0. 0. 1.0 5.0011 0.105 1.0 1.0 1.0 0.0
 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *  There are some assumptions that go into using this format that may not
 *  be obvious.  The first is that only particles with status code = 1
 *  are tracked in the LArSoft/Geant4 combination making the mother daughter
 *  relations somewhat irrelevant.  That also means that you should let
 *  Geant4 handle any decays.
 *
 *  The units in LArSoft are cm for distances and ns for time.
 *  The use of `TLorentzVector` below does not imply space and time have the same units
 *   (do not use `TLorentzVector::Boost()`).
 */
#include <string>
#include <fstream>

#include "art/Framework/Core/EDProducer.h"
#include "art/Framework/Core/ModuleMacros.h"
#include "art/Framework/Principal/Event.h"
#include "fhiclcpp/ParameterSet.h"
#include "cetlib_except/exception.h"
#include "messagefacility/MessageLogger/MessageLogger.h"

#include "TLorentzVector.h"

#include "larcore/Geometry/Geometry.h"
#include "larcoreobj/SummaryData/RunData.h"
#include "nusimdata/SimulationBase/MCTruth.h"
#include "nusimdata/SimulationBase/MCParticle.h"

namespace evgen {
  class TextFileGen;
}

class evgen::TextFileGen : public art::EDProducer {
public:
  explicit TextFileGen(fhicl::ParameterSet const & p);

  void produce(art::Event & e)                    override;
  void beginJob()                                 override;
  void beginRun(art::Run & run)                   override;

private:

  std::ifstream* fInputFile;
  std::string    fInputFileName; ///< Name of text file containing events to simulate
  double fMoveY; ///< Project particles to a new y plane.
};

//------------------------------------------------------------------------------
evgen::TextFileGen::TextFileGen(fhicl::ParameterSet const & p)
  : EDProducer{p}
  , fInputFile(0)
  , fInputFileName{p.get<std::string>("InputFileName")}
  , fMoveY{p.get<double>("MoveY", -1e9)}

{
  if (fMoveY>-1e8){
    mf::LogWarning("TextFileGen")<<"Particles will be moved to a new plane y = "<<fMoveY<<" cm.\n";
  }

  produces< std::vector<simb::MCTruth>   >();
  produces< sumdata::RunData, art::InRun >();
}

//------------------------------------------------------------------------------
void evgen::TextFileGen::beginJob()
{
  fInputFile = new std::ifstream(fInputFileName.c_str());

  // check that the file is a good one
  if( !fInputFile->good() )
    throw cet::exception("TextFileGen") << "input text file "
                                        << fInputFileName
                                        << " cannot be read.\n";
}

//------------------------------------------------------------------------------
void evgen::TextFileGen::beginRun(art::Run& run)
{
    art::ServiceHandle<geo::Geometry const> geo;
    run.put(std::make_unique<sumdata::RunData>(geo->DetectorName()));
  }

//------------------------------------------------------------------------------
void evgen::TextFileGen::produce(art::Event & e)
{
  // check that the file is still good
  if( !fInputFile->good() )
    throw cet::exception("TextFileGen") << "input text file "
                                        << fInputFileName
                                        << " cannot be read in produce().\n";


  std::unique_ptr< std::vector<simb::MCTruth> > truthcol(new std::vector<simb::MCTruth>);
  simb::MCTruth truth;

  // declare the variables for reading in the event record
  int            event          = 0;
  unsigned short nParticles     = 0;
  int            status         = 0;
  int            pdg            = 0;
  int            firstMother    = 0;
  int            secondMother   = 0;
  int            firstDaughter  = 0;
  int            secondDaughter = 0;
  double         xMomentum      = 0.;
  double         yMomentum      = 0.;
  double         zMomentum      = 0.;
  double         energy         = 0.;
  double         mass           = 0.;
  double         xPosition      = 0.;
  double         yPosition      = 0.;
  double         zPosition      = 0.;
  double         time           = 0.;

  // read in line to get event number and number of particles
  std::string oneLine;
  std::getline(*fInputFile, oneLine);
  std::istringstream inputLine;
  inputLine.str(oneLine);

  inputLine >> event >> nParticles;

  // now read in all the lines for the particles
  // in this interaction. only particles with
  // status = 1 get tracked in Geant4.
  for(unsigned short i = 0; i < nParticles; ++i){
    std::getline(*fInputFile, oneLine);
    inputLine.clear();
    inputLine.str(oneLine);

    inputLine >> status      >> pdg
              >> firstMother >> secondMother >> firstDaughter >> secondDaughter
              >> xMomentum   >> yMomentum    >> zMomentum     >> energy >> mass
              >> xPosition   >> yPosition    >> zPosition     >> time;

    //Project the particle to a new y plane
    if (fMoveY>-1e8){
      double totmom = sqrt(pow(xMomentum,2)+pow(yMomentum,2)+pow(zMomentum,2));
      double kx = xMomentum/totmom;
      double ky = yMomentum/totmom;
      double kz = zMomentum/totmom;
      if (ky){
        double l = (fMoveY-yPosition)/ky;
        xPosition += kx*l;
        yPosition += ky*l;
        zPosition += kz*l;
      }
    }

    TLorentzVector pos(xPosition, yPosition, zPosition, time);
    TLorentzVector mom(xMomentum, yMomentum, zMomentum, energy);

    simb::MCParticle part(i, pdg, "primary", firstMother, mass, status);
    part.AddTrajectoryPoint(pos, mom);

    truth.Add(part);
  }

  truthcol->push_back(truth);

  e.put(std::move(truthcol));
}

DEFINE_ART_MODULE(evgen::TextFileGen)