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 "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtVector3R.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenModels/EvtOmegaDalitz.hh"
#include "EvtGenBase/EvtReport.hh"
#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 ;
   
}