Geant4IsotropeGenerator.cpp

// $Id: $
//==========================================================================
//  AIDA Detector description implementation for LCD
//--------------------------------------------------------------------------
// Copyright (C) Organisation europeenne pour la Recherche nucleaire (CERN)
// All rights reserved.
//
// For the licensing terms see $DD4hepINSTALL/LICENSE.
// For the list of contributors see $DD4hepINSTALL/doc/CREDITS.
//
// Author     : M.Frank
//
//==========================================================================

// Framework include files
#include "DD4hep/Printout.h"
#include "DD4hep/InstanceCount.h"
#include "DDG4/Geant4Random.h"
#include "DDG4/Geant4IsotropeGenerator.h"

using namespace std;
using namespace DD4hep::Simulation;

/// Standard constructor
Geant4IsotropeGenerator::Geant4IsotropeGenerator(Geant4Context* ctxt, const string& nam)
  : Geant4ParticleGenerator(ctxt, nam)
{
  InstanceCount::increment(this);
  declareProperty("PhiMin", m_phiMin = 0.0);
  declareProperty("PhiMax", m_phiMax = 2.0*M_PI);
  declareProperty("ThetaMin", m_thetaMin = 0.0);
  declareProperty("ThetaMax", m_thetaMax = M_PI);
}

/// Default destructor
Geant4IsotropeGenerator::~Geant4IsotropeGenerator() {
  InstanceCount::decrement(this);
}

/// Particle modification. Caller presets defaults to: ( direction = m_direction, momentum = m_energy)
void Geant4IsotropeGenerator::getParticleDirection(int, ROOT::Math::XYZVector& direction, double& momentum) const   {
  Geant4Event& evt = context()->event();
  Geant4Random& rnd = evt.random();
  double phi   = m_phiMin+(m_phiMax-m_phiMin)*rnd.rndm();
  double theta = m_thetaMin+(m_thetaMax-m_thetaMin)*rnd.rndm();
  double x1 = std::sin(theta)*std::cos(phi);
  double x2 = std::sin(theta)*std::sin(phi);
  double x3 = std::cos(theta);

  direction.SetXYZ(x1,x2,x3);
  momentum = rnd.rndm()*momentum;
}