/home/bes3soft/bes3soft/Boss/7.0.2/dist/7.0.2/Generator/BesEvtGen/BesEvtGen-00-03-58/src/EvtGen/EvtGenModels/EvtPartWave.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) 2000      Caltech, UCSB
//
// Module: EvtHelAmp.cc
//
// Description: Decay model for implementation of generic 2 body
//              decay specified by the partial wave amplitudes
//
//
// Modification history:
//
//    fkw        February 2, 2001     changes to satisfy KCC
//    RYD       September 7, 2000       Module created
//
//------------------------------------------------------------------------
// 
#include "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtVector4C.hh"
#include "EvtGenBase/EvtTensor4C.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenModels/EvtPartWave.hh"
#include "EvtGenBase/EvtEvalHelAmp.hh"
#include "EvtGenBase/EvtId.hh"
#include <string>
#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtKine.hh"
#include "EvtGenBase/EvtCGCoefSingle.hh"
#include <algorithm>
using std::endl;
EvtPartWave::~EvtPartWave() {}

void EvtPartWave::getName(std::string& model_name){

  model_name="PARTWAVE";     

}


EvtDecayBase* EvtPartWave::clone(){

  return new EvtPartWave;

}

void EvtPartWave::init(){

  checkNDaug(2);

  //find out how many states each particle have
  int _nA=EvtSpinType::getSpinStates(EvtPDL::getSpinType(getParentId()));
  int _nB=EvtSpinType::getSpinStates(EvtPDL::getSpinType(getDaug(0)));
  int _nC=EvtSpinType::getSpinStates(EvtPDL::getSpinType(getDaug(1)));

  if (verbose()){
    report(INFO,"EvtGen")<<"_nA,_nB,_nC:"
                         <<_nA<<","<<_nB<<","<<_nC<<endl;
  }

  //find out what 2 times the spin is
  int _JA2=EvtSpinType::getSpin2(EvtPDL::getSpinType(getParentId()));
  int _JB2=EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(0)));
  int _JC2=EvtSpinType::getSpin2(EvtPDL::getSpinType(getDaug(1)));

  if (verbose()){
    report(INFO,"EvtGen")<<"_JA2,_JB2,_JC2:"
                         <<_JA2<<","<<_JB2<<","<<_JC2<<endl;
  }


  //allocate memory
  int* _lambdaA2=new int[_nA];
  int* _lambdaB2=new int[_nB];
  int* _lambdaC2=new int[_nC];

  EvtComplexPtr* _HBC=new EvtComplexPtr[_nB];
  int ib,ic;
  for(ib=0;ib<_nB;ib++){
    _HBC[ib]=new EvtComplex[_nC];
  }


  int i;
  //find the allowed helicities (actually 2*times the helicity!)

  fillHelicity(_lambdaA2,_nA,_JA2);
  fillHelicity(_lambdaB2,_nB,_JB2);
  fillHelicity(_lambdaC2,_nC,_JC2);

  if (verbose()){
    report(INFO,"EvtGen")<<"Helicity states of particle A:"<<endl;
    for(i=0;i<_nA;i++){
      report(INFO,"EvtGen")<<_lambdaA2[i]<<endl;
    }

    report(INFO,"EvtGen")<<"Helicity states of particle B:"<<endl;
    for(i=0;i<_nB;i++){
      report(INFO,"EvtGen")<<_lambdaB2[i]<<endl;
    }

    report(INFO,"EvtGen")<<"Helicity states of particle C:"<<endl;
    for(i=0;i<_nC;i++){
      report(INFO,"EvtGen")<<_lambdaC2[i]<<endl;
    }

    report(INFO,"EvtGen")<<"Will now figure out the valid (M_LS) states:"<<endl;

  }

  int Lmin=std::max(_JA2-_JB2-_JC2,std::max(_JB2-_JA2-_JC2,_JC2-_JA2-_JB2));
  if (Lmin<0) Lmin=0;
  //int Lmin=_JA2-_JB2-_JC2;
  int Lmax=_JA2+_JB2+_JC2;

  int L;

  int _nPartialWaveAmp=0;

  int _nL[50];
  int _nS[50];

  for (L=Lmin;L<=Lmax;L+=2){
    int Smin=abs(L-_JA2);
    if (Smin<abs(_JB2-_JC2)) Smin=abs(_JB2-_JC2);
    int Smax=L+_JA2;
    if (Smax>abs(_JB2+_JC2)) Smax=abs(_JB2+_JC2);
    int S;
    for (S=Smin;S<=Smax;S+=2){
      _nL[_nPartialWaveAmp]=L;
      _nS[_nPartialWaveAmp]=S;

      _nPartialWaveAmp++;
      if (verbose()){
        report(INFO,"EvtGen")<<"M["<<L<<"]["<<S<<"]"<<endl;    
      }
    }
  }

  checkNArg(_nPartialWaveAmp*2);

  int argcounter=0;

  EvtComplex _M[50];

  for(i=0;i<_nPartialWaveAmp;i++){
    _M[i]=getArg(argcounter)*exp(EvtComplex(0.0,getArg(argcounter+1)));;
    argcounter+=2;
    if (verbose()){
      report(INFO,"EvtGen")<<"M["<<_nL[i]<<"]["<<_nS[i]<<"]="<<_M[i]<<endl;
    }
  }

  //Now calculate the helicity amplitudes

  

  for(ib=0;ib<_nB;ib++){
    for(ic=0;ic<_nC;ic++){
      _HBC[ib][ic]=0.0;
      if (abs(_lambdaB2[ib]-_lambdaC2[ic])<=_JA2){
        for(i=0;i<_nPartialWaveAmp;i++){
          int L=_nL[i];
          int S=_nS[i];
          int lambda2=_lambdaB2[ib];
          int lambda3=_lambdaC2[ic];
          int s1=_JA2;
          int s2=_JB2;
          int s3=_JC2;
          int m1=lambda2-lambda3;
          EvtCGCoefSingle c1(s2,s3);
          EvtCGCoefSingle c2(L,S);

          if (verbose()){
            report(INFO,"EvtGen") << "s2,lambda2:"<<s2<<" "<<lambda2<<endl;
          }
          //fkw changes to satisfy KCC
          double fkwTmp = (L+1.0)/(s1+1.0);

          if (S>=abs(m1)){

            EvtComplex tmp=sqrt(fkwTmp)
              *c1.coef(S,m1,s2,s3,lambda2,-lambda3)
              *c2.coef(s1,m1,L,S,0,m1)*_M[i];
            //fkw EvtComplex tmp=sqrt((L+1)/(s1+1))*c1.coef(S,m1,s2,s3,lambda2,-lambda3)*c2.coef(s1,m1,L,S,0,m1)*_M[i];
            _HBC[ib][ic]+=tmp;
          }
        }
        if (verbose()){
          report(INFO,"EvtGen")<<"_HBC["<<ib<<"]["<<ic<<"]="<<_HBC[ib][ic]<<endl;
        }
      }
    }
  }

  _evalHelAmp=new EvtEvalHelAmp(EvtPDL::getSpinType(getParentId()),
                                EvtPDL::getSpinType(getDaug(0)),
                                EvtPDL::getSpinType(getDaug(1)),
                                _HBC);


}


void EvtPartWave::initProbMax(){

  double maxprob=_evalHelAmp->probMax();

  if (verbose()){
    report(INFO,"EvtGen")<<"Calculated probmax"<<maxprob<<endl;
  }

  setProbMax(maxprob);

}


void EvtPartWave::decay( EvtParticle *p){

  //first generate simple phase space
  p->initializePhaseSpace(getNDaug(),getDaugs());

  _evalHelAmp->evalAmp(p,_amp2);

  return;

}



void EvtPartWave::fillHelicity(int* lambda2,int n,int J2){
  
  int i;
  
  //photon is special case!
  if (n==2&&J2==2) {
    lambda2[0]=2;
    lambda2[1]=-2;
    return;
  }
  
  assert(n==J2+1);

  for(i=0;i<n;i++){
    lambda2[i]=n-i*2-1;
  }

  return;

}

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