//
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#ifndef G4NeutronHPThermalBoost_h
#define G4NeutronHPThermalBoost_h

#include "G4HadProjectile.hh"
#include "G4Element.hh"
#include "G4ReactionProduct.hh"
#include "G4Nucleus.hh"
#include "G4NucleiPropertiesTable.hh"
#include "G4Electron.hh"
#include "G4Neutron.hh"

class G4NeutronHPThermalBoost
{
public: 
  G4double GetThermalEnergy(const G4HadProjectile & aP, 
                            const G4Element * anE, 
			    G4double aT)
  {
    G4double theA = anE->GetN();
    G4double theZ = anE->GetZ();
    return GetThermalEnergy(aP, theA ,theZ, aT);
  }
  			    
  G4double GetThermalEnergy(const G4HadProjectile & aP, 
                            G4double theA, G4double theZ,
			    G4double aT)
  {
    // prepare neutron
    G4double eKinetic = aP.GetKineticEnergy();
    G4ReactionProduct theNeutron( const_cast<G4ParticleDefinition *>(aP.GetDefinition()) );
    theNeutron.SetMomentum( aP.Get4Momentum().vect() );
    theNeutron.SetKineticEnergy( eKinetic );
    G4ThreeVector neuVelo = (1./aP.GetDefinition()->GetPDGMass())*theNeutron.GetMomentum();

    // prepare properly biased thermal nucleus
    G4Nucleus aNuc;
    G4double eps = 0.0001;
    G4double eleMass; 
    eleMass = ( G4NucleiPropertiesTable::GetNuclearMass(static_cast<G4int>(theZ+eps), static_cast<G4int>(theA+eps))
  	       ) / G4Neutron::Neutron()->GetPDGMass();
  
    G4ReactionProduct aThermalNuc = aNuc.GetBiasedThermalNucleus(eleMass, neuVelo, aT);
    
    // boost to rest system and return
    G4ReactionProduct boosted;
    boosted.Lorentz(theNeutron, aThermalNuc);
    return boosted.GetKineticEnergy();
  }
};
#endif