AliDecayer realisation for the EvtGen code and EvtGen itself.

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

#include "EvtGenBase/EvtPatches.hh"
 
#include <stdlib.h>
#include <math.h>
#include "EvtGenBase/EvtVector4R.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenModels/EvtPhiDalitz.hh"
#include "EvtGenBase/EvtReport.hh"
#include <string>

// Implementation of KLOE measurement
// PL B561: 55-60 (2003) + Erratum B609:449-450 (2005)
// or hep-ex/0303016v2

 
EvtPhiDalitz::~EvtPhiDalitz() {}

std::string EvtPhiDalitz::getName(){

  return "PHI_DALITZ";     

}


EvtDecayBase* EvtPhiDalitz::clone(){

  return new EvtPhiDalitz;

}

void EvtPhiDalitz::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);

  _mRho=0.7758;
  _gRho=0.1439;
  _aD=0.78;
  _phiD=-2.47;
  _aOmega=0.0071;
  _phiOmega=-0.22;

  _locPip=-1;
  _locPim=-1;
  _locPi0=-1;

  for ( int i=0; i<3; i++) {
     if ( getDaug(i) == EvtPDL::getId("pi+")) _locPip=i;
     if ( getDaug(i) == EvtPDL::getId("pi-")) _locPim=i;
     if ( getDaug(i) == EvtPDL::getId("pi0")) _locPi0=i;
  }
  if ( _locPip == -1 || _locPim == -1 || _locPi0 == -1 ) {
    report(ERROR,"EvtGen") << getModelName() << "generator expects daughters to be pi+ pi- pi0\n";
    report(ERROR,"EvtGen") << "Found " << EvtPDL::name(getDaug(0)) << " " 
			   << EvtPDL::name(getDaug(1)) << " " 
			   << EvtPDL::name(getDaug(2)) << std::endl;

  }


}
    



void EvtPhiDalitz::decay( EvtParticle *p){

  EvtId PIP=EvtPDL::getId("pi+");
  EvtId PIM=EvtPDL::getId("pi-");
  EvtId PIZ=EvtPDL::getId("pi0");
  EvtId OMEGA=EvtPDL::getId("omega");

  p->initializePhaseSpace(getNDaug(),getDaugs());

  EvtVector4R Ppip = p->getDaug(_locPip)->getP4();
  EvtVector4R Ppim = p->getDaug(_locPim)->getP4();
  EvtVector4R Ppi0 = p->getDaug(_locPi0)->getP4();
  EvtVector4R Qp = (Ppim + Ppi0);
  EvtVector4R Qm = (Ppip + Ppi0);
  EvtVector4R Q0 = (Ppip + Ppim);
  double m2_pip = pow(EvtPDL::getMeanMass(PIP),2); 
  double m2_pim = pow(EvtPDL::getMeanMass(PIM),2);
  double m2_pi0 = pow(EvtPDL::getMeanMass(PIZ),2);
  double M2rhop = pow(_mRho,2);
  double M2rhom = pow(_mRho,2);
  double M2rho0 = pow(_mRho,2);
  double M2omega = pow(EvtPDL::getMeanMass(OMEGA),2);

  double Wrhop = _gRho;
  double Wrhom = _gRho;
  double Wrho0 = _gRho;
  double Womega = EvtPDL::getWidth(OMEGA);
    
  EvtComplex Atot(0,0);

  //Rho+ Risonance Amplitude
  double Gp = Wrhop*pow(((Qp.mass2()-m2_pim-m2_pi0)/2-M2rhop/4)/(M2rhop/4-(m2_pim+m2_pi0)/2),3/2)*(M2rhop/Qp.mass2());
  EvtComplex Drhop((Qp.mass2()-M2rhop),Qp.mass()*Gp);
  EvtComplex A1(M2rhop/Drhop);

  //Rho- Risonance Amplitude
  double Gm = Wrhom*pow(((Qm.mass2()-m2_pip-m2_pi0)/2-M2rhom/4)/(M2rhom/4-(m2_pip+m2_pi0)/2),3/2)*(M2rhom/Qm.mass2());
  EvtComplex Drhom((Qm.mass2()-M2rhom),Qm.mass()*Gm);
  EvtComplex A2(M2rhom/Drhom);

  //Rho0 Risonance Amplitude
  double G0 = Wrho0*pow(((Q0.mass2()-m2_pip-m2_pim)/2-M2rho0/4)/(M2rho0/4-(m2_pip+m2_pim)/2),3/2)*(M2rho0/Q0.mass2());
  EvtComplex Drho0((Q0.mass2()-M2rho0),Q0.mass()*G0);
  EvtComplex A3(M2rho0/Drho0);
 
  //Omega Risonance Amplitude
  EvtComplex OmegaPhase(0,_phiOmega);    
  EvtComplex DOmega((Q0.mass2()-M2omega),Q0.mass()*Womega);
  EvtComplex A4(_aOmega*M2omega*exp(OmegaPhase)/DOmega);

  //Direct Decay Amplitude
  EvtComplex DirPhase(0,_phiD);
  EvtComplex A5(_aD*exp(DirPhase));

  Atot=A1+A2+A3+A4+A5;

  vertex(0,Atot);
  vertex(1,Atot);
  vertex(2,Atot);

  return ;
   
}