EvtOmegaDalitz.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: EvtOmegaDalitz.cc
//
// Description: Routine to decay omega -> pi pi pi0
//
// Modification history:
//
//    RYD     November 24, 1996         Module created
//
//------------------------------------------------------------------------
//
#include "EvtOmegaDalitz.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtTensor4C.hh"
#include "../EvtGenBase/EvtVector3R.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <stdlib.h>
#include <string>
 
EvtOmegaDalitz::~EvtOmegaDalitz() {}
 
void EvtOmegaDalitz::getName( std::string& model_name ) { model_name = "OMEGA_DALITZ"; }
 
EvtDecayBase* EvtOmegaDalitz::clone() { return new EvtOmegaDalitz; }
 
void EvtOmegaDalitz::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 3 );
 
  checkSpinParent( EvtSpinType::VECTOR );
 
  checkSpinDaughter( 0, EvtSpinType::SCALAR );
  checkSpinDaughter( 1, EvtSpinType::SCALAR );
  checkSpinDaughter( 2, EvtSpinType::SCALAR );
}
 
void EvtOmegaDalitz::initProbMax() { setProbMax( 1.0 ); }
 
void EvtOmegaDalitz::decay( EvtParticle* p ) {
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  EvtVector4C ep[3];
 
  ep[0] = p->eps( 0 );
  ep[1] = p->eps( 1 );
  ep[2] = p->eps( 2 );
 
  EvtVector4R mompi1 = p->getDaug( 0 )->getP4();
  EvtVector4R mompi2 = p->getDaug( 1 )->getP4();
 
  EvtVector3R p1( mompi1.get( 1 ), mompi1.get( 2 ), mompi1.get( 3 ) );
  EvtVector3R p2( mompi2.get( 1 ), mompi2.get( 2 ), mompi2.get( 3 ) );
  EvtVector3R q = cross( p2, p1 );
 
  EvtVector3C e1( ep[0].get( 1 ), ep[0].get( 2 ), ep[0].get( 3 ) );
  EvtVector3C e2( ep[1].get( 1 ), ep[1].get( 2 ), ep[1].get( 3 ) );
  EvtVector3C e3( ep[2].get( 1 ), ep[2].get( 2 ), ep[2].get( 3 ) );
 
  // This is an approximate formula of the maximum value that
  //|q| can have.
  double norm = 1.14 / ( p->mass() * p->mass() / 9.0 - mompi1.mass2() );
 
  vertex( 0, norm * e1 * q );
  vertex( 1, norm * e2 * q );
  vertex( 2, norm * e3 * q );
 
  return;
}