EvtPyGaGa.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 1998      Caltech, UCSB
//
// Module: EvtPycont.cc
//
// Description: Routine to generate e+e- --> q\barq  via Jetset
//
// Modification history:
//
//    PCK     August 4, 1997        Module created
//    RS      October 28, 2002      copied from EvtJscont.cc
//
//------------------------------------------------------------------------
//
#include "EvtPyGaGa.hh"
#include "../EvtGenBase/EvtDecayBase.hh"
#include "../EvtGenBase/EvtDecayTable.hh"
#include "../EvtGenBase/EvtId.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "EvtPythia.hh"
#include <iostream>
#include <stdlib.h>
#include <string.h>
 
extern "C" {
extern void pystat_( int& );
}
 
extern "C" struct {
  int dc[18];
} decaych_;
 
EvtPyGaGa::~EvtPyGaGa() {
  int i = 1;
  pystat_( i );
}
 
void EvtPyGaGa::getName( std::string& model_name ) { model_name = "PYGAGA"; }
 
EvtDecayBase* EvtPyGaGa::clone() { return new EvtPyGaGa; }
 
void EvtPyGaGa::init() {
  // check that there are 1 argument
  checkNArg( 0 );
  for ( int i = 0; i < 18; i++ ) decaych_.dc[i] = 0;
}
 
void EvtPyGaGa::initProbMax() { noProbMax(); }
 
void EvtPyGaGa::decay( EvtParticle* p ) {
  EvtPythia::pythiaInit( 1 );
  EvtVector4R p4[100];
 
  double energy = p->mass();
 
  int   i, more;
  int   ndaugjs;
  int   kf[100];
  EvtId id[100];
  int   type[MAX_DAUG];
 
  double px[100], py[100], pz[100], e[100];
 
  if ( p->getNDaug() != 0 ) { return; }
  do {
    EvtPythia::pythiacont( &energy, &ndaugjs, kf, px, py, pz, e );
 
    for ( i = 0; i < ndaugjs; i++ )
    {
 
      id[i] = EvtPDL::evtIdFromStdHep( kf[i] );
 
      type[i] = EvtPDL::getSpinType( id[i] );
 
      // have to protect against negative mass^2 for massless particles
      // i.e. neutrinos and photons.
      // this is uggly but I need to fix it right now....
 
      if ( px[i] * px[i] + py[i] * py[i] + pz[i] * pz[i] >= e[i] * e[i] )
        e[i] = sqrt( px[i] * px[i] + py[i] * py[i] + pz[i] * pz[i] ) + 0.0000000000001;
 
      p4[i].set( e[i], px[i], py[i], pz[i] );
    }
 
    int channel = EvtDecayTable::inChannelList( p->getId(), ndaugjs, id );
 
    more = ( ( channel != -1 ) && ( channel != p->getChannel() ) );
 
  } while ( more );
 
  p->makeDaughters( ndaugjs, id );
 
  for ( i = 0; i < ndaugjs; i++ ) p->getDaug( i )->init( id[i], p4[i] );
 
  return;
}