Merge branch 'master' of https://git.cern.ch/reps/AliRoot

[u/mrichter/AliRoot.git] / TEvtGen / EvtGenModels / EvtOmegaDalitz.cxx

//--------------------------------------------------------------------------
//
// 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() {}

std::string EvtOmegaDalitz::getName(){

  return "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 ;
   
}