EvtSVS.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: EvtSVS.cc
//
// Description: Routine to decay scalar -> vector + scalar
//
// Modification history:
//
//    RYD       November 24, 1996       Module created
//
//------------------------------------------------------------------------
//
#include "EvtSVS.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <stdlib.h>
#include <string>
 
EvtSVS::~EvtSVS() {}
 
void EvtSVS::getName( std::string& model_name ) { model_name = "SVS"; }
 
EvtDecayBase* EvtSVS::clone() { return new EvtSVS; }
 
void EvtSVS::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::SCALAR );
 
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
}
 
void EvtSVS::initProbMax() { setProbMax( 1.0 ); }
 
void EvtSVS::decay( EvtParticle* p ) {
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
  // report(INFO,"EvtGen") << "par " << p->getP4() << " " << p->getDaug(0)->getP4() << " " <<
  //   p->getDaug(1)->getP4() << " " << p->mass() << " " <<
  //   p->getDaug(0)->mass() << " " << p->getDaug(1)->mass() <<endl;
  EvtParticle* v;
  v                     = p->getDaug( 0 );
  double      massv     = v->mass();
  EvtVector4R momv      = v->getP4();
  EvtVector4R moms      = p->getDaug( 1 )->getP4();
  double      m_parent  = p->mass();
  EvtVector4R p4_parent = momv + moms;
 
  double norm = massv / ( momv.d3mag() * m_parent );
  p4_parent   = norm * p4_parent;
  vertex( 0, p4_parent * ( v->epsParent( 0 ) ) );
  vertex( 1, p4_parent * ( v->epsParent( 1 ) ) );
  vertex( 2, p4_parent * ( v->epsParent( 2 ) ) );
 
  return;
}