evgen::TextFileGen Class Reference

Inheritance diagram for evgen::TextFileGen:

Public Member Functions
	TextFileGen (fhicl::ParameterSet const &p)
void	produce (art::Event &e) override
void	beginJob () override
void	beginRun (art::Run &run) override

Private Member Functions
std::pair< unsigned, unsigned >	readEventInfo (std::istream &is)
simb::MCTruth	readNextHepEvt ()

Private Attributes
unsigned long int	fOffset
std::ifstream *	fInputFile
std::string	fInputFileName
	Name of text file containing events to simulate. More...
double	fMoveY
	Project particles to a new y plane. More...

Detailed Description

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()).

Definition at line 83 of file TextFileGen_module.cc.

Constructor & Destructor Documentation

evgen::TextFileGen::TextFileGen ( fhicl::ParameterSet const &  p )

explicit

Definition at line 102 of file TextFileGen_module.cc.

  : EDProducer{p}
  , fOffset{p.get<unsigned long int>("Offset")}
  , 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 >();


}

Member Function Documentation

void evgen::TextFileGen::beginJob ( )

override

Definition at line 120 of file TextFileGen_module.cc.

{
  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";


  for (unsigned i = 0; i != fOffset; ++i) {
    auto const [eventNo, nparticles] = readEventInfo(*fInputFile);
    for (unsigned p = 0; p != nparticles; ++p) {
       constexpr auto all_chars_until = std::numeric_limits<unsigned>::max();
       fInputFile->ignore(all_chars_until, '\n');
    }
  }


}

void evgen::TextFileGen::beginRun ( art::Run &  run )

override

Definition at line 143 of file TextFileGen_module.cc.

{
    art::ServiceHandle<geo::Geometry const> geo;
    run.put(std::make_unique<sumdata::RunData>(geo->DetectorName()));
  }

void evgen::TextFileGen::produce ( art::Event &  e )

override

Definition at line 150 of file TextFileGen_module.cc.

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




//Now, read the Event to be used.



// check that the file is still good
  if( !fInputFile->good() )
    throw cet::exception("TextFileGen") << "input text file "
                                        << fInputFileName
                                        << " cannot be read in produce().\n";
   auto truthcol = std::make_unique<std::vector<simb::MCTruth>>();
   truthcol->push_back(readNextHepEvt());


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

std::pair< unsigned, unsigned > evgen::TextFileGen::readEventInfo ( std::istream &  is )

private

Definition at line 254 of file TextFileGen_module.cc.

{
  std::string line;
  getline(iss, line);
  std::istringstream buffer{line};

  // Parse read line for the event number and particles per event
  unsigned event, nparticles;
  buffer >> event >> nparticles;
  return {event, nparticles};
}

simb::MCTruth evgen::TextFileGen::readNextHepEvt ( )

private

Definition at line 180 of file TextFileGen_module.cc.

{

  // declare the variables for reading in the event record
  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::istringstream inputLine;
  simb::MCTruth nextEvent;
  auto const [eventNo, nParticles] = readEventInfo(*fInputFile);



  // 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);

    nextEvent.Add(part);

  }  //  end loop on particles.

return nextEvent;
}

Member Data Documentation

std::ifstream* evgen::TextFileGen::fInputFile

private

Definition at line 96 of file TextFileGen_module.cc.

std::string evgen::TextFileGen::fInputFileName

private

Name of text file containing events to simulate.

Definition at line 97 of file TextFileGen_module.cc.

double evgen::TextFileGen::fMoveY

private

Project particles to a new y plane.

Definition at line 98 of file TextFileGen_module.cc.

unsigned long int evgen::TextFileGen::fOffset

private

Definition at line 95 of file TextFileGen_module.cc.

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The documentation for this class was generated from the following file:

• TextFileGen_module.cc