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// $Id: G4QCoherentChargeExchange.cc,v 1.8 2009/02/23 09:49:24 mkossov Exp $
// GEANT4 tag $Name: geant4-09-03-beta-cand-01 $
//
//      ---------------- G4QCoherentChargeExchange class -----------------
//                 by Mikhail Kossov, December 2003.
// G4QCoherentChargeExchange class of the CHIPS Simulation Branch in GEANT4
// ---------------------------------------------------------------
// ****************************************************************************************
// ********** This CLASS is temporary moved from the photolepton_hadron directory *********
// ****************************************************************************************
// Short description: This class resolves an ambiguity in the definition of the
// "inelastic" cross section. As it was shown in Ph.D.Thesis (M.Kosov,ITEP,1979)
// it is more reasonable to subdivide the total cross-section in the coherent &
// incoherent parts, but the measuring method for the "inelastic" cross-sections
// consideres the lack of the projectile within the narrow forward solid angle
// with the consequent extrapolation of these partial cross-sections, corresponding
// to the particular solid angle, to the zero solid angle. The low angle region
// is shadowed by the elastic (coherent) scattering. BUT the coherent charge
// exchange (e.g. conversion p->n) is included by this procedure as a constant term
// in the extrapolation, so the "inelastic" cross-section differes from the
// incoherent cross-section by the value of the coherent charge exchange cross
// section. Fortunately, this cross-sectoion drops ruther fast with energy increasing.
// All Geant4 inelastic hadronic models (including CHIPS) simulate the incoherent
// reactions. So the incoherent (including quasielastic) cross-section must be used
// instead of the inelastic cross-section. For that the "inelastic" cross-section
// must be reduced by the value of the coherent charge-exchange cross-section, which
// is estimated (it must be tuned!) in this CHIPS class. The angular distribution
// is made (at present) identical to the corresponding coherent-elastic scattering 
// -----------------------------------------------------------------------------------
//#define debug
//#define pdebug
//#define tdebug
//#define nandebug
//#define ppdebug

#include "G4QCoherentChargeExchange.hh"

// Initialization of static vectors
G4int    G4QCoherentChargeExchange::nPartCWorld=152;  // #of particles initialized in CHIPS
std::vector<G4int> G4QCoherentChargeExchange::ElementZ; // Z of element(i) in theLastCalc
std::vector<G4double> G4QCoherentChargeExchange::ElProbInMat; // SumProbOfElem in Material
std::vector<std::vector<G4int>*> G4QCoherentChargeExchange::ElIsoN;// N of isotope(j), E(i)
std::vector<std::vector<G4double>*>G4QCoherentChargeExchange::IsoProbInEl;//SumProbIsotE(i)

// Constructor
G4QCoherentChargeExchange::G4QCoherentChargeExchange(const G4String& processName)
  : G4VDiscreteProcess(processName, fHadronic)
{
#ifdef debug
  G4cout<<"G4QCohChargeEx::Constructor is called processName="<<processName<<G4endl;
#endif
  if (verboseLevel>0) G4cout << GetProcessName() << " process is created "<< G4endl;
  SetProcessSubType(fChargeExchange);
  //G4QCHIPSWorld::Get()->GetParticles(nPartCWorld); // Create CHIPS World (234 part. max)
}

// Destructor
G4QCoherentChargeExchange::~G4QCoherentChargeExchange() {}


G4LorentzVector G4QCoherentChargeExchange::GetEnegryMomentumConservation()
                                                                {return EnMomConservation;}

G4int G4QCoherentChargeExchange::GetNumberOfNeutronsInTarget() {return nOfNeutrons;}

// output of the function must be in units of length! L=1/sig_V,sig_V=SUM(n(j,i)*sig(j,i)),
// where n(i,j) is a number of nuclei of the isotop j of the element i in V=1(lengtUnit^3)
// ********** All CHIPS cross sections are calculated in the surface units ************
G4double G4QCoherentChargeExchange::GetMeanFreePath(const G4Track& aTrack,G4double Q,
                                                    G4ForceCondition* Fc)
{
  *Fc = NotForced;
  const G4DynamicParticle* incidentParticle = aTrack.GetDynamicParticle();
  G4ParticleDefinition* incidentParticleDefinition=incidentParticle->GetDefinition();
  if( !IsApplicable(*incidentParticleDefinition))
    G4cout<<"*W*G4QCohChargeEx::GetMeanFreePath called for notImplementedParticle"<<G4endl;
  // Calculate the mean Cross Section for the set of Elements(*Isotopes) in the Material
  G4double Momentum = incidentParticle->GetTotalMomentum(); // 3-momentum of the Particle
#ifdef debug
  G4double KinEn = incidentParticle->GetKineticEnergy();
  G4cout<<"G4QCohChEx::GetMeanFreePath: kinE="<<KinEn<<",Mom="<<Momentum<<G4endl; // Result
#endif
  const G4Material* material = aTrack.GetMaterial();        // Get the current material
  const G4double* NOfNucPerVolume = material->GetVecNbOfAtomsPerVolume();
  const G4ElementVector* theElementVector = material->GetElementVector();
  G4int nE=material->GetNumberOfElements();
#ifdef debug
  G4cout<<"G4QCohChargeExchange::GetMeanFreePath:"<<nE<<" Elem's in theMaterial"<<G4endl;
#endif
  G4int pPDG=0;

  if     (incidentParticleDefinition == G4Proton::Proton()  ) pPDG=2212;
  else if(incidentParticleDefinition == G4Neutron::Neutron()) pPDG=2112;
  else G4cout<<"G4QCohChargeEx::GetMeanFreePath: only nA & pA are implemented"<<G4endl;
  
  G4QIsotope* Isotopes = G4QIsotope::Get(); // Pointer to the G4QIsotopes singleton
  G4double sigma=0.;                        // Sums over elements for the material
  G4int IPIE=IsoProbInEl.size();            // How many old elements?
  if(IPIE) for(G4int ip=0; ip<IPIE; ++ip)   // Clean up the SumProb's of Isotopes (SPI)
  {
    std::vector<G4double>* SPI=IsoProbInEl[ip]; // Pointer to the SPI vector
    SPI->clear();
    delete SPI;
    std::vector<G4int>* IsN=ElIsoN[ip];     // Pointer to the N vector
    IsN->clear();
    delete IsN;
  }
  ElProbInMat.clear();                      // Clean up the SumProb's of Elements (SPE)
  ElementZ.clear();                         // Clear the body vector for Z of Elements
  IsoProbInEl.clear();                      // Clear the body vector for SPI
  ElIsoN.clear();                           // Clear the body vector for N of Isotopes
  for(G4int i=0; i<nE; ++i)
  {
    G4Element* pElement=(*theElementVector)[i]; // Pointer to the current element
    G4int Z = static_cast<G4int>(pElement->GetZ()); // Z of the Element
    ElementZ.push_back(Z);                  // Remember Z of the Element
    G4int isoSize=0;                        // The default for the isoVectorLength is 0
    G4int indEl=0;                          // Index of non-natural element or 0(default)
    G4IsotopeVector* isoVector=pElement->GetIsotopeVector(); // Get the predefined IsoVect
    if(isoVector) isoSize=isoVector->size();// Get size of the existing isotopeVector
#ifdef debug
    G4cout<<"G4QCoherentChargeExchange::GetMeanFreePath:isovectorLength="<<isoSize<<G4endl;
#endif
    if(isoSize)                             // The Element has non-trivial abundance set
    {
      indEl=pElement->GetIndex()+1;         // Index of the non-trivial element is an order
#ifdef debug
      G4cout<<"G4QCCX::GetMFP: iE="<<indEl<<", def="<<Isotopes->IsDefined(Z,indEl)<<G4endl;
#endif
      if(!Isotopes->IsDefined(Z,indEl))     // This index is not defined for this Z: define
      {
        std::vector<std::pair<G4int,G4double>*>* newAbund =
                                               new std::vector<std::pair<G4int,G4double>*>;
        G4double* abuVector=pElement->GetRelativeAbundanceVector();
        for(G4int j=0; j<isoSize; j++)      // Calculation of abundance vector for isotopes
        {
          G4int N=pElement->GetIsotope(j)->GetN()-Z; // N means A=N+Z !
          if(pElement->GetIsotope(j)->GetZ()!=Z)G4cerr<<"G4QCohChX::GetMeanFreePath: Z="
                                         <<pElement->GetIsotope(j)->GetZ()<<"#"<<Z<<G4endl;
          G4double abund=abuVector[j];
          std::pair<G4int,G4double>* pr= new std::pair<G4int,G4double>(N,abund);
#ifdef debug
          G4cout<<"G4QCohChEx::GetMeanFreePath:pair#="<<j<<",N="<<N<<",ab="<<abund<<G4endl;
#endif
          newAbund->push_back(pr);
        }
#ifdef debug
        G4cout<<"G4QCohChEx::GetMeanFreePath: pairVectorLength="<<newAbund->size()<<G4endl;
#endif
        indEl=G4QIsotope::Get()->InitElement(Z,indEl,newAbund); // definition of the newInd
        for(G4int k=0; k<isoSize; k++) delete (*newAbund)[k];   // Cleaning temporary
        delete newAbund; // Was "new" in the beginning of the name space
      }
    }
    std::vector<std::pair<G4int,G4double>*>* cs= Isotopes->GetCSVector(Z,indEl);//CSPointer
    std::vector<G4double>* SPI = new std::vector<G4double>; // Pointer to the SPI vector
    IsoProbInEl.push_back(SPI);
    std::vector<G4int>* IsN = new std::vector<G4int>; // Pointer to the N vector
    ElIsoN.push_back(IsN);
    G4int nIs=cs->size();                   // A#Of Isotopes in the Element
#ifdef debug
    G4cout<<"G4QCohChargEx::GMFP:=***=>,#isot="<<nIs<<", Z="<<Z<<", indEl="<<indEl<<G4endl;
#endif
    G4double susi=0.;                       // sum of CS over isotopes
    if(nIs) for(G4int j=0; j<nIs; j++)      // Calculate CS for eachIsotope of El
    {
      std::pair<G4int,G4double>* curIs=(*cs)[j]; // A pointer, which is used twice
      G4int N=curIs->first;                 // #of Neuterons in the isotope j of El i
      IsN->push_back(N);                    // Remember Min N for the Element
#ifdef debug
      G4cout<<"G4QCCX::GMFP:true, P="<<Momentum<<",Z="<<Z<<",N="<<N<<",PDG="<<pPDG<<G4endl;
#endif
      G4bool ccsf=true;
      if(Q==-27.) ccsf=false;
#ifdef debug
      G4cout<<"G4QCoherentChargeExchange::GMFP: GetCS #1 j="<<j<<G4endl;
#endif
      G4double CSI=CalculateXSt(ccsf, true, Momentum, Z, N, pPDG);// CS(j,i) for theIsotope

#ifdef debug
      G4cout<<"G4QCohChEx::GetMeanFreePath:jI="<<j<<",Zt="<<Z<<",Nt="<<N<<",Mom="<<Momentum
            <<", XSec="<<CSI/millibarn<<G4endl;
#endif
      curIs->second = CSI;
      susi+=CSI;                            // Make a sum per isotopes
      SPI->push_back(susi);                 // Remember summed cross-section
    } // End of temporary initialization of the cross sections in the G4QIsotope singeltone
    sigma+=Isotopes->GetMeanCrossSection(Z,indEl)*NOfNucPerVolume[i];//SUM(MeanCS*NOfNperV)
#ifdef debug
    G4cout<<"G4QCohChEx::GMFP:<S>="<<Isotopes->GetMeanCrossSection(Z,indEl)<<",AddToSigma="
          <<Isotopes->GetMeanCrossSection(Z,indEl)*NOfNucPerVolume[i]<<G4endl;
#endif
    ElProbInMat.push_back(sigma);
  } // End of LOOP over Elements
  // Check that cross section is not zero and return the mean free path
#ifdef debug
  G4cout<<"G4QCoherentChargeExchange::GetMeanFreePath: MeanFreePath="<<1./sigma<<G4endl;
#endif
  if(sigma > 0.) return 1./sigma;                 // Mean path [distance] 
  return DBL_MAX;
}

G4bool G4QCoherentChargeExchange::IsApplicable(const G4ParticleDefinition& particle) 
{
  if      (particle == *(        G4Proton::Proton()        )) return true;
  else if (particle == *(       G4Neutron::Neutron()       )) return true;
  //else if (particle == *(     G4MuonMinus::MuonMinus()     )) return true; 
  //else if (particle == *(       G4TauPlus::TauPlus()       )) return true;
  //else if (particle == *(      G4TauMinus::TauMinus()      )) return true;
  //else if (particle == *(      G4Electron::Electron()      )) return true;
  //else if (particle == *(      G4Positron::Positron()      )) return true;
  //else if (particle == *(         G4Gamma::Gamma()         )) return true;
  //else if (particle == *(      G4MuonPlus::MuonPlus()      )) return true;
  //else if (particle == *(G4AntiNeutrinoMu::AntiNeutrinoMu())) return true;
  //else if (particle == *(   G4NeutrinoMu::NeutrinoMu()   )) return true;
  //else if (particle == *(     G4PionMinus::PionMinus()     )) return true;
  //else if (particle == *(      G4PionPlus::PionPlus()      )) return true;
  //else if (particle == *(      G4KaonPlus::KaonPlus()      )) return true;
  //else if (particle == *(     G4KaonMinus::KaonMinus()     )) return true;
  //else if (particle == *(  G4KaonZeroLong::KaonZeroLong()  )) return true;
  //else if (particle == *( G4KaonZeroShort::KaonZeroShort() )) return true;
  //else if (particle == *(        G4Lambda::Lambda()        )) return true;
  //else if (particle == *(     G4SigmaPlus::SigmaPlus()     )) return true;
  //else if (particle == *(    G4SigmaMinus::SigmaMinus()    )) return true;
  //else if (particle == *(     G4SigmaZero::SigmaZero()     )) return true;
  //else if (particle == *(       G4XiMinus::XiMinus()       )) return true;
  //else if (particle == *(        G4XiZero::XiZero()        )) return true;
  //else if (particle == *(    G4OmegaMinus::OmegaMinus()    )) return true;
  //else if (particle == *(   G4AntiNeutron::AntiNeutron()   )) return true;
  //else if (particle == *(    G4AntiProton::AntiProton()    )) return true;
#ifdef debug
  G4cout<<"***>>G4QCoherChargeExch::IsApplicable: PDG="<<particle.GetPDGEncoding()<<G4endl;
#endif
  return false;
}

G4VParticleChange* G4QCoherentChargeExchange::PostStepDoIt(const G4Track& track,
                                                           const G4Step& step)
{
  static const G4double mProt= G4QPDGCode(2212).GetMass();     // CHIPS pMass in MeV
  static const G4double mNeut= G4QPDGCode(2212).GetMass();     // CHIPS pMass in MeV
  //
  //-------------------------------------------------------------------------------------
  static G4bool CWinit = true;                       // CHIPS Warld needs to be initted
  if(CWinit)
  {
    CWinit=false;
    G4QCHIPSWorld::Get()->GetParticles(nPartCWorld); // Create CHIPS World (234 part.max)
  }
  //-------------------------------------------------------------------------------------
  const G4DynamicParticle* projHadron = track.GetDynamicParticle();
  const G4ParticleDefinition* particle=projHadron->GetDefinition();
#ifdef debug
  G4cout<<"G4QCohChargeExchange::PostStepDoIt: Before the GetMeanFreePath is called In4M="
        <<projHadron->Get4Momentum()<<" of PDG="<<particle->GetPDGEncoding()<<", Type="
        <<particle->GetParticleType()<<", Subtp="<<particle->GetParticleSubType()<<G4endl;
#endif
  G4ForceCondition cond=NotForced;
  GetMeanFreePath(track, -27., &cond);                  // @@ ?? jus to update parameters?
#ifdef debug
  G4cout<<"G4QCohChargeExchange::PostStepDoIt: After GetMeanFreePath is called"<<G4endl;
#endif
  G4LorentzVector proj4M=(projHadron->Get4Momentum())/MeV; // Convert to MeV!
  G4double momentum = projHadron->GetTotalMomentum()/MeV; // 3-momentum of the Proj in MeV
  G4double Momentum = proj4M.rho();                   // @@ Just for the test purposes
  if(std::fabs(Momentum-momentum)>.000001)
       G4cerr<<"*Warning*G4QCohChEx::PostStepDoIt:P(IU)="<<Momentum<<"#"<<momentum<<G4endl;
#ifdef pdebug
  G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: pP(IU)="<<Momentum<<"="<<momentum
        <<",pM="<<pM<<",proj4M="<<proj4M<<proj4M.m()<<G4endl;
#endif
  if (!IsApplicable(*particle))  // Check applicability
  {
    G4cerr<<"G4QCoherentChargeExchange::PostStepDoIt: Only NA is implemented."<<G4endl;
    return 0;
  }
  const G4Material* material = track.GetMaterial();      // Get the current material
  G4int Z=0;
  const G4ElementVector* theElementVector = material->GetElementVector();
  G4int nE=material->GetNumberOfElements();
#ifdef debug
  G4cout<<"G4QCohChargeExchange::PostStepDoIt: "<<nE<<" elements in the material."<<G4endl;
#endif
  G4int projPDG=0;                           // PDG Code prototype for the captured hadron
  // Not all these particles are implemented yet (see Is Applicable)
  if      (particle ==          G4Proton::Proton()         ) projPDG= 2212;
  else if (particle ==         G4Neutron::Neutron()        ) projPDG= 2112;
  //else if (particle ==       G4PionMinus::PionMinus()      ) projPDG= -211;
  //else if (particle ==        G4PionPlus::PionPlus()       ) projPDG=  211;
  //else if (particle ==        G4KaonPlus::KaonPlus()       ) projPDG= 2112;
  //else if (particle ==       G4KaonMinus::KaonMinus()      ) projPDG= -321;
  //else if (particle ==    G4KaonZeroLong::KaonZeroLong()   ) projPDG=  130;
  //else if (particle ==   G4KaonZeroShort::KaonZeroShort()  ) projPDG=  310;
  //else if (particle ==        G4MuonPlus::MuonPlus()       ) projPDG=  -13;
  //else if (particle ==       G4MuonMinus::MuonMinus()      ) projPDG=   13;
  //else if (particle ==      G4NeutrinoMu::NeutrinoMu()     ) projPDG=   14;
  //else if (particle ==  G4AntiNeutrinoMu::AntiNeutrinoMu() ) projPDG=  -14;
  //else if (particle ==        G4Electron::Electron()       ) projPDG=   11;
  //else if (particle ==        G4Positron::Positron()       ) projPDG=  -11;
  //else if (particle ==       G4NeutrinoE::NeutrinoE()      ) projPDG=   12;
  //else if (particle ==   G4AntiNeutrinoE::AntiNeutrinoE()  ) projPDG=  -12;
  //else if (particle ==           G4Gamma::Gamma()          ) projPDG=   22;
  //else if (particle ==         G4TauPlus::TauPlus()        ) projPDG=  -15;
  //else if (particle ==        G4TauMinus::TauMinus()       ) projPDG=   15;
  //else if (particle ==     G4NeutrinoTau::NeutrinoTau()    ) projPDG=   16;
  //else if (particle == G4AntiNeutrinoTau::AntiNeutrinoTau()) projPDG=  -16;
  //else if (particle ==          G4Lambda::Lambda()         ) projPDG= 3122;
  //else if (particle ==       G4SigmaPlus::SigmaPlus()      ) projPDG= 3222;
  //else if (particle ==      G4SigmaMinus::SigmaMinus()     ) projPDG= 3112;
  //else if (particle ==       G4SigmaZero::SigmaZero()      ) projPDG= 3212;
  //else if (particle ==         G4XiMinus::XiMinus()        ) projPDG= 3312;
  //else if (particle ==          G4XiZero::XiZero()         ) projPDG= 3322;
  //else if (particle ==      G4OmegaMinus::OmegaMinus()     ) projPDG= 3334;
  //else if (particle ==     G4AntiNeutron::AntiNeutron()    ) projPDG=-2112;
  //else if (particle ==      G4AntiProton::AntiProton()     ) projPDG=-2212;
#ifdef debug
  G4int prPDG=particle->GetPDGEncoding();
  G4cout<<"G4QCohChrgExchange::PostStepDoIt: projPDG="<<projPDG<<", stPDG="<<prPDG<<G4endl;
#endif
  if(!projPDG)
  {
    G4cerr<<"*Warning*G4QCoherentChargeExchange::PostStepDoIt:UndefinedProjHadron"<<G4endl;
    return 0;
  }
  //G4double pM2=proj4M.m2();        // in MeV^2
  //G4double pM=std::sqrt(pM2);      // in MeV
  G4double pM=mNeut;
  G4int    fPDG=2112;
  if(projPDG==2112)
  {
    pM=mProt;
    fPDG=2212;
  }
  G4double pM2=pM*pM;
  // Element treatment
  G4int EPIM=ElProbInMat.size();
#ifdef debug
  G4cout<<"G4QCohChEx::PostStDoIt:m="<<EPIM<<",n="<<nE<<",T="<<ElProbInMat[EPIM-1]<<G4endl;
#endif
  G4int i=0;
  if(EPIM>1)
  {
    G4double rnd = ElProbInMat[EPIM-1]*G4UniformRand();
    for(i=0; i<nE; ++i)
    {
#ifdef debug
      G4cout<<"G4QCohChEx::PostStepDoIt:EPM["<<i<<"]="<<ElProbInMat[i]<<",r="<<rnd<<G4endl;
#endif
      if (rnd<ElProbInMat[i]) break;
    }
    if(i>=nE) i=nE-1;                        // Top limit for the Element
  }
  G4Element* pElement=(*theElementVector)[i];
  Z=static_cast<G4int>(pElement->GetZ());
#ifdef debug
    G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: i="<<i<<", Z(element)="<<Z<<G4endl;
#endif
  if(Z<=0)
  {
    G4cerr<<"-Warning-G4QCoherentChargeExchange::PostStepDoIt: Element with Z="<<Z<<G4endl;
    if(Z<0) return 0;
  }
  std::vector<G4double>* SPI = IsoProbInEl[i];// Vector of summedProbabilities for isotopes
  std::vector<G4int>* IsN = ElIsoN[i];     // Vector of "#of neutrons" in the isotope El[i]
  G4int nofIsot=SPI->size();               // #of isotopes in the element i
#ifdef debug
  G4cout<<"G4QCohChargeExchange::PosStDoIt:nI="<<nofIsot<<",T="<<(*SPI)[nofIsot-1]<<G4endl;
#endif
  G4int j=0;
  if(nofIsot>1)
  {
    G4double rndI=(*SPI)[nofIsot-1]*G4UniformRand(); // Randomize the isotop of the Element
    for(j=0; j<nofIsot; ++j)
    {
#ifdef debug
      G4cout<<"G4QCohChargEx::PostStepDoIt: SP["<<j<<"]="<<(*SPI)[j]<<", r="<<rndI<<G4endl;
#endif
      if(rndI < (*SPI)[j]) break;
    }
    if(j>=nofIsot) j=nofIsot-1;            // Top limit for the isotope
  }
  G4int N =(*IsN)[j]; ;                    // Randomized number of neutrons
#ifdef debug
  G4cout<<"G4QCohChargeEx::PostStepDoIt: j="<<i<<", N(isotope)="<<N<<", MeV="<<MeV<<G4endl;
#endif
  if(N<0)
  {
    G4cerr<<"*Warning*G4QCohChEx::PostStepDoIt: Isotope with Z="<<Z<<", 0>N="<<N<<G4endl;
    return 0;
  }
  nOfNeutrons=N;                           // Remember it for the energy-momentum check
#ifdef debug
  G4cout<<"G4QCohChargeExchange::PostStepDoIt: N="<<N<<" for element with Z="<<Z<<G4endl;
#endif
  if(N<0)
  {
    G4cerr<<"*Warning*G4QCoherentChargeExchange::PostStepDoIt:Element with N="<<N<< G4endl;
    return 0;
  }
  aParticleChange.Initialize(track);
#ifdef debug
  G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: track is initialized"<<G4endl;
#endif
  G4double      weight    = track.GetWeight();
  G4double      localtime = track.GetGlobalTime();
  G4ThreeVector position  = track.GetPosition();
#ifdef debug
  G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: before Touchable extraction"<<G4endl;
#endif
  G4TouchableHandle trTouchable = track.GetTouchableHandle();
#ifdef debug
  G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: Touchable is extracted"<<G4endl;
#endif
  //
  G4int targPDG=90000000+Z*1000+N;         // CHIPS PDG Code of the target nucleus
  if(projPDG==2212) targPDG+=999;          // convert to final nucleus code
  else if(projPDG==2112) targPDG-=999;
  G4QPDGCode targQPDG(targPDG);            // @@ use G4Ion and get rid of CHIPS World
  G4double tM=targQPDG.GetMass();          // CHIPS final nucleus mass in MeV
  G4double kinEnergy= projHadron->GetKineticEnergy()*MeV; // Kin energy in MeV (Is *MeV n?)
  G4ParticleMomentum dir = projHadron->GetMomentumDirection();// It is a unit three-vector
  G4LorentzVector tot4M=proj4M+G4LorentzVector(0.,0.,0.,tM); // Total 4-mom of the reaction
#ifdef debug
  G4cout<<"G4QCohChrgEx::PostStepDoIt: tM="<<tM<<", p4M="<<proj4M<<", t4M="<<tot4M<<G4endl;
#endif
  EnMomConservation=tot4M;                 // Total 4-mom of reaction for E/M conservation
  // @@ Probably this is not necessary any more
#ifdef debug
  G4cout<<"G4QCCX::PSDI:false, P="<<Momentum<<",Z="<<Z<<",N="<<N<<",PDG="<<projPDG<<G4endl;
#endif
  G4double xSec=CalculateXSt(false, true, Momentum, Z, N, projPDG); // Recalc. CrossSection
#ifdef debug
  G4cout<<"G4QCoChEx::PSDI:PDG="<<projPDG<<",P="<<Momentum<<",CS="<<xSec/millibarn<<G4endl;
#endif
#ifdef nandebug
  if(xSec>0. || xSec<0. || xSec==0);
  else  G4cout<<"*Warning*G4QCohChargeExchange::PSDI: xSec="<<xSec/millibarn<<G4endl;
#endif
  // @@ check a possibility to separate p, n, or alpha (!)
  if(xSec <= 0.) // The cross-section iz 0 -> Do Nothing
  {
#ifdef pdebug
    G4cerr<<"*Warning*G4QCoherentChargeExchange::PSDoIt:*Zero cross-section* PDG="<<projPDG
          <<",tPDG="<<targPDG<<",P="<<Momentum<<G4endl;
#endif
    //Do Nothing Action insead of the reaction
    aParticleChange.ProposeEnergy(kinEnergy);
    aParticleChange.ProposeLocalEnergyDeposit(0.);
    aParticleChange.ProposeMomentumDirection(dir) ;
    return G4VDiscreteProcess::PostStepDoIt(track,step);
  }
  G4double mint=CalculateXSt(false, false, Momentum, Z, N, projPDG);// randomize t in MeV^2
#ifdef pdebug
  G4cout<<"G4QCohChEx::PoStDoIt:pPDG="<<projPDG<<",tPDG="<<targPDG<<",P="<<Momentum<<",CS="
        <<xSec<<",-t="<<mint<<G4endl;
#endif
#ifdef nandebug
  if(mint>-.0000001);
  else  G4cout<<"*Warning*G4QCoherentChargeExchange::PostStDoIt:-t="<<mint<<G4endl;
#endif
  G4double maxt=CalculateXSt(true, false, Momentum, Z, N, projPDG);
  if(maxt<=0.) maxt=1.e-27;
  G4double cost=1.-mint/maxt; // cos(theta) in CMS (@@ we neglect mass diff for ChEx)
  // 
#ifdef ppdebug
  G4cout<<"G4QCoherentChargeExchange::PoStDoIt:t="<<mint<<",dpcm2="<<maxt
        <<",Ek="<<kinEnergy<<",tM="<<tM<<",pM="<<pM<<",cost="<<cost<<G4endl;
#endif
  if(cost>1. || cost<-1. || !(cost>-1. || cost<1.))
  {
    if(cost>1.000001 || cost<-1.000001 || !(cost>-1. || cost<1.))
    {
      G4double tM2=tM*tM;                         // Squared target mass
      G4double pEn=pM+kinEnergy;                  // tot projectile Energy in MeV
      G4double sM=(tM+tM)*pEn+tM2+pM2;            // Mondelstam s
      G4double twop2cm=(tM2+tM2)*(pEn*pEn-pM2)/sM;// Max_t/2 (2*p^2_cm)
      G4cout<<"*Warning*G4QCohChEx::PostStepDoIt:cos="<<cost<<",t="<<mint<<",T="<<kinEnergy
            <<",tM="<<tM<<",tmax="<<2*kinEnergy*tM<<",p="<<projPDG<<",t="<<targPDG<<G4endl;
      G4cout<<"..G4QCohChEx::PoStDoI: dpcm2="<<twop2cm<<"="<<maxt<<G4endl;
    }
    if     (cost>1.)  cost=1.;
    else if(cost<-1.) cost=-1.;
  }
  G4LorentzVector reco4M=G4LorentzVector(0.,0.,0.,tM);      // 4mom of the recoil target
  G4LorentzVector scat4M=G4LorentzVector(0.,0.,0.,pM);      // 4mom of the recoil target
  G4LorentzVector dir4M=tot4M-G4LorentzVector(0.,0.,0.,(tot4M.e()-tM-pM)*.01);
  if(!G4QHadron(tot4M).RelDecayIn2(scat4M, reco4M, dir4M, cost, cost))
  {
    G4cerr<<"G4QCohChEx::PSDI:t4M="<<tot4M<<",pM="<<pM<<",tM="<<tM<<",cost="<<cost<<G4endl;
    //G4Exception("G4QCoherentChargeExchange::PostStepDoIt:","009",FatalException,"Decay");
  }
#ifdef debug
  G4cout<<"G4QCohChEx::PoStDoIt:s4M="<<scat4M<<"+r4M="<<reco4M<<"="<<scat4M+reco4M<<G4endl;
  G4cout<<"G4QCohChEx::PoStDoIt: scatE="<<scat4M.e()-pM<<", recoE="<<reco4M.e()-tM<<",d4M="
        <<tot4M-scat4M-reco4M<<G4endl;
#endif
  // Kill scattered hadron
  aParticleChange.ProposeTrackStatus(fStopAndKill);
  // Definition of the scattered nucleon
  G4DynamicParticle* theSec = new G4DynamicParticle; // A secondary for the recoil hadron 
  G4ParticleDefinition* theDefinition=G4Proton::Proton();
  if(projPDG==2212) theDefinition=G4Neutron::Neutron();
  theSec->SetDefinition(theDefinition);
  EnMomConservation-=scat4M;
  theSec->Set4Momentum(scat4M);
  G4Track* aNewTrack = new G4Track(theSec, localtime, position );
  aNewTrack->SetWeight(weight);                                   //    weighted
  aNewTrack->SetTouchableHandle(trTouchable);
  aParticleChange.AddSecondary( aNewTrack );
  // Filling the recoil nucleus
  theSec = new G4DynamicParticle; // A secondary for the recoil hadron 
  G4int aA = Z+N;
#ifdef pdebug
  G4cout<<"G4QCoherentChargeExchange::PostStepDoIt: Ion Z="<<Z<<", A="<<aA<<G4endl;
#endif
  theDefinition=G4ParticleTable::GetParticleTable()->FindIon(Z,aA,0,Z);
  if(!theDefinition)G4cout<<"*Warning*G4QCohChEx::PostStepDoIt:drop PDG="<<targPDG<<G4endl;
#ifdef pdebug
  G4cout<<"G4QCohChEx::PostStepDoIt:RecoilName="<<theDefinition->GetParticleName()<<G4endl;
#endif
  theSec->SetDefinition(theDefinition);
  EnMomConservation-=reco4M;
#ifdef tdebug
  G4cout<<"G4QCohChEx::PostSDoIt:"<<targPDG<<reco4M<<reco4M.m()<<EnMomConservation<<G4endl;
#endif
  theSec->Set4Momentum(reco4M);
#ifdef debug
  G4ThreeVector curD=theSec->GetMomentumDirection();
  G4double curM=theSec->GetMass();
  G4double curE=theSec->GetKineticEnergy()+curM;
  G4cout<<"G4QCohChEx::PostStpDoIt:p="<<curD<<curD.mag()<<",e="<<curE<<",m="<<curM<<G4endl;
#endif
  // Make a recoil nucleus
  aNewTrack = new G4Track(theSec, localtime, position );
  aNewTrack->SetWeight(weight);                                   //    weighted
  aNewTrack->SetTouchableHandle(trTouchable);
  aParticleChange.AddSecondary( aNewTrack );
#ifdef debug
    G4cout<<"G4QCoherentChargeExchange::PostStepDoIt:*** PostStepDoIt is done ***"<<G4endl;
#endif
  return G4VDiscreteProcess::PostStepDoIt(track, step);
}

G4double G4QCoherentChargeExchange::CalculateXSt(G4bool oxs, G4bool xst, G4double p,
                                                 G4int Z, G4int N, G4int pPDG) 
{
  static G4bool init=false;
  static G4bool first=true;
  static G4VQCrossSection* CSmanager;
  G4QuasiFreeRatios* qfMan=G4QuasiFreeRatios::GetPointer();
  if(first)                              // Connection with a singletone
  {
    CSmanager=G4QElasticCrossSection::GetPointer();
    first=false;
  }
  G4double res=0.;
  if(oxs && xst)                         // Only the Cross-Section can be returened
  {
    res=CSmanager->GetCrossSection(true, p, Z, N, pPDG); // XS for isotope
    res*=qfMan->ChExElCoef(p*MeV, Z, N, pPDG);
  }
  else if(!oxs && xst)                   // Calculate Cross-Section & prepare differential
  {
    res=CSmanager->GetCrossSection(false, p, Z, N, pPDG);// XS for isotope + init t-distr.
    res*=qfMan->ChExElCoef(p*MeV, Z, N, pPDG);
    // The XS for the nucleus must be calculated the last
    init=true;
  }
  else if(init)                          // Return t-value for scattering (=G4QElastic)
  {
    if(oxs) res=CSmanager->GetHMaxT();   // Calculate the max_t value
    else res=CSmanager->GetExchangeT(Z, N, pPDG); // fanctionally randomized -t in MeV^2
  }
  else G4cout<<"*Warning*G4QCohChrgExchange::CalculateXSt: NotInitiatedScattering"<<G4endl;
  return res;
}