EvtS2GV.cc

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//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of models developed at BES collaboration
//      based on the EvtGen framework.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/BesCopyright
//      Copyright (A) 2006      Ping Rong-Gang @IHEP
//
// Module:  EvtS2GV.cc
//
// Description: Routine to decay chi_c1-> gamma J/psi  using
//    helicity amplitude, assuming E1 dominance.
// Modification history:
//
//    Ping R.-G.       December, 2006       Module created
//
//------------------------------------------------------------------------
//
#include "EvtS2GV.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtHelSys.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtRandom.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include "../EvtGenBase/EvtVector4R.hh"
#include <stdlib.h>
#include <string>
using std::endl;
 
EvtS2GV::~EvtS2GV() {}
 
void EvtS2GV::getName( std::string& model_name ) { model_name = "S2GV"; }
 
EvtDecayBase* EvtS2GV::clone() { return new EvtS2GV; }
 
void EvtS2GV::init() {
  static EvtId GAM = EvtPDL::getId( "gamma" );
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 2 );
  checkSpinParent( EvtSpinType::SCALAR );
  checkSpinDaughter( 0, EvtSpinType::PHOTON );
  checkSpinDaughter( 1, EvtSpinType::VECTOR );
  if ( !( getDaug( 0 ) == GAM ) )
  {
    report( ERROR, "EvtGen" ) << "EvtS2GV generator radiative decays expected " << endl;
    ::abort();
  }
}
 
void EvtS2GV::initProbMax() {
 
  // Hard coded... should not be hard to calculate...
  setProbMax( 2.0001 );
}
 
void EvtS2GV::decay( EvtParticle* p ) {
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  double     phs = 0.;
  EvtComplex F11 = exp( EvtComplex( 0, phs ) );
 
  vertex( 0, 0, F11 );
  vertex( 0, 2, 0 );
  vertex( 0, 1, 0 );
  vertex( 1, 0, 0 );
  vertex( 1, 2, 0 );
  vertex( 1, 1, -F11 );
  return;
}