MpPlace.cc

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#include "MuonProphet.h"

// Put a spallation background to position
void MuonProphet::setPosition(HepMC::GenEvent& event, HepMC::ThreeVector& aPoint )
{
  HepMC::FourVector position(aPoint.x(),
                             aPoint.y(),
                             aPoint.z(),
                             0);

  HepMC::GenEvent::vertex_iterator vtx, done = event.vertices_end();
  for (vtx = event.vertices_begin(); vtx != done; ++vtx) {

    // still use the original vertex time
    position.setT( (*vtx)->position().t() );

    (*vtx)->set_position(position);
  }

}


// Set a spallation background to right time
void MuonProphet::setTime(HepMC::GenEvent& event, double t0, double lifetime)
{
  // Use negtive lifetime to skip the exponential random lifetime

  //
  // debug()<<"t0= "<<t0<<endreq;
  //
  double dt = 0;

  if(lifetime<0) {
    dt=0;
  } else {
    double u = m_rnd.Rndm();
    // Exponential Distribution: t(n) = t(n-1) * exp(-t/tL)
    dt = ((-1.0 * log(u)) * lifetime);
  }

  dt = dt / CLHEP::nanosecond;

  HepMC::GenEvent::vertex_iterator vtx, done = event.vertices_end();
  for (vtx = event.vertices_begin(); vtx != done; ++vtx) {

    HepMC::FourVector position = (*vtx)->position();

    // relative to muon + mother particle's lifetime + internal delay
    double vertex_time = t0+dt+position.t();

    position.setT(vertex_time);
    (*vtx)->set_position(position);
  }
}