BeamHaloGenerator.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "BeamHaloGenerator/BeamHaloGenerator.h"
#include "BeamHaloGenerator/BeamHaloParticleBuffer.h"
#include "BeamHaloGenerator/BeamHaloGeneratorAlg.h"
#include "BeamHaloGenerator/AsciiInput.h"
#include "BeamHaloGenerator/BeamHaloGeneratorSettings.h"
#include "AtlasHepMC/GenEvent.h"
#include "CLHEP/Random/RandFlat.h"
#include "CLHEP/Units/PhysicalConstants.h"
#include "TMath.h"
#include <cmath>
 
BeamHaloGenerator::BeamHaloGenerator(const HepPDT::ParticleDataTable* particleTable,
                     const std::string& inputFile,
                     const std::vector<std::string>& generatorSettings):
  m_particleTable(particleTable),
  m_inputFile(inputFile),
  m_interfacePlane(0.),
  m_enableFlip(false),
  m_flipProbability(0.),
  m_enableSampling(false),
  m_bufferFileName("buffer.bin"),
  m_eventNumber(0),
  m_debug(false),
  m_generatorSettings(generatorSettings) {
  for(int i=0;i<NUM_COUNTERS;i++) {
    m_counters[i] = 0;
    m_wsums[i] = 0.;
  }
}
 
//------------------------------------------------------------------
 
BeamHaloGenerator::~BeamHaloGenerator() {
}
 
//------------------------------------------------------------------
 
int BeamHaloGenerator::genInitialize() {
  m_asciiInput = std::make_unique<AsciiInput>(m_inputFile);
  m_beamHaloGeneratorSettings = std::make_unique< BeamHaloGeneratorSettings>(m_generatorSettings);
 
  return 0;
}
 
//------------------------------------------------------------------
 
int BeamHaloGenerator::genFinalize() {
 
  std::cout << "=================================================================" << std::endl;
  std::cout << "|                                 | Total Number | Total Weight |" << std::endl;
  std::cout << "|---------------------------------------------------------------|" << std::endl;
  std::cout << "| Particles read from input file  | ";
  std::cout << std::setw(12) << m_counters[TOT_READ] << " | ";
  std::cout << std::setw(12) << std::setprecision(8) << m_wsums[TOT_READ] << " |" << std::endl;
  std::cout << "| Particles after cuts            | ";
  std::cout << std::setw(12) << m_counters[TOT_AFTER] << " | ";
  std::cout << std::setw(12) << std::setprecision(8) << m_wsums[TOT_AFTER] << " |" << std::endl;
  std::cout << "| Particles generated             | ";
  std::cout << std::setw(12) << m_counters[TOT_GEN] << " | ";
  std::cout << std::setw(12) << std::setprecision(8) << m_wsums[TOT_GEN] << " |" << std::endl;
  std::cout << "=================================================================" << std::endl;
  
  std::cout << std::setprecision(6);
 
  return 0;
}
 
//------------------------------------------------------------------
 
bool BeamHaloGenerator::flipEvent(CLHEP::HepRandomEngine* engine) {
  if(!m_enableFlip) return false;
 
  // Check to see if the event should be flipped or not
  if(CLHEP::RandFlat::shoot(engine) <= m_flipProbability) {
    if(m_debug) std::cout << "Debug: Flipping event" << std::endl;
    return true;
  }
 
  return false;
}
 
//------------------------------------------------------------------
 
int BeamHaloGenerator::convertEvent(std::vector<BeamHaloParticle>* beamHaloEvent,
                                    HepMC::GenEvent* evt,
                                    CLHEP::HepRandomEngine* engine) {
  double pz;
  bool flipFlag = flipEvent(engine);
  HepMC::GenParticlePtr genParticle;
  HepMC::GenVertexPtr genVertex;
  const double c = 2.99792458E+11; // speed of light in mm/s
 
  std::vector<BeamHaloParticle>::iterator itr = beamHaloEvent->begin();
  std::vector<BeamHaloParticle>::iterator itr_end = beamHaloEvent->end();
 
  if(itr != itr_end) {
    // Take the primary information from the first particle in the event.  If the event is more than one
    // particle, the particles come from the same primary proton.
    evt->weights().push_back((*itr).weight()); // event weight
    HepMC::FourVector primaryPosition = (*itr).positionAtPrimary();
    evt->weights().push_back(primaryPosition.x()); // Starting position of primary particle: x position (cm)
    evt->weights().push_back(primaryPosition.y()); // Starting position of primary particle: y position (cm)
    evt->weights().push_back(primaryPosition.z()); // Starting position of primary particle: z position (cm)
    evt->weights().push_back(primaryPosition.t()); // Starting position of primary particle: t (s)
  } 
 
  // Append each particle to the GenEvent
  for(;itr!=itr_end;++itr) {
    HepMC::FourVector position = (*itr).positionAtScoringPlane();
    HepMC::FourVector fourVector = (*itr).fourVector();
 
    if(!flipFlag) {
      genParticle = HepMC::newGenParticlePtr(fourVector,
                       (*itr).pdgId(),
                       1);
 
      genVertex = HepMC::newGenVertexPtr(HepMC::FourVector(position.x(),
                             position.y(),
                             (position.z() + m_interfacePlane),
                             c*position.t() -1.0*std::fabs(m_interfacePlane)),
                       1);
    }
    else {
      pz = fourVector.pz();
      fourVector.setPz(-pz);
 
      genParticle = HepMC::newGenParticlePtr(fourVector,
                       (*itr).pdgId(),
                       1);
 
      genVertex = HepMC::newGenVertexPtr(HepMC::FourVector(position.x(),
                             position.y(),
                             -1.0*(position.z() + m_interfacePlane),
                             c*position.t() -1.0*std::fabs(m_interfacePlane)),
                       1);
    }
 
    genVertex->add_particle_out(genParticle);
    evt->add_vertex(genVertex);
  }
 
  return 0;
}
 
//------------------------------------------------------------------