G4ScreeningMottCrossSection Class Reference

#include <G4ScreeningMottCrossSection.hh>

Public Member Functions
	G4ScreeningMottCrossSection ()
virtual	~G4ScreeningMottCrossSection ()
void	Initialise (const G4ParticleDefinition *, G4double cosThetaLim)
G4double	GetScreeningAngle ()
void	SetScreeningCoefficient ()
void	SetupParticle (const G4ParticleDefinition *)
void	SetupKinematic (G4double kinEnergy, G4double Z)
G4double	NuclearCrossSection (G4int form)
G4ThreeVector	GetNewDirection ()
G4double	GetMom2CM () const
G4double	GetMom2Lab () const
G4double	GetTrec () const
G4double	GetScreeningCoefficient () const
G4double	GetTotalCross () const
G4double	McFcorrection (G4double)
G4double	RatioMottRutherford (G4double)
G4double	FormFactor2ExpHof (G4double)
G4double	FormFactor2Gauss (G4double)
G4double	FormFactor2UniformHelm (G4double)
G4double	GetScatteringAngle ()
G4double	AngleDistribution (G4double)

Detailed Description

Definition at line 88 of file G4ScreeningMottCrossSection.hh.

Constructor & Destructor Documentation

G4ScreeningMottCrossSection::G4ScreeningMottCrossSection ( )

explicit

Definition at line 86 of file G4ScreeningMottCrossSection.cc.

                                                        :
   cosThetaMin(1.0),
   cosThetaMax(-1.0),
   alpha(fine_structure_const),
   htc2(hbarc_squared),
   e2(electron_mass_c2*classic_electr_radius)
{
  TotalCross=0;

  fNistManager = G4NistManager::Instance();
  fG4pow = G4Pow::GetInstance();
  particle=nullptr;

  spin = mass = mu_rel=0.0;
  tkinLab = momLab2 = invbetaLab2=0.0;
  tkin = mom2 = invbeta2=beta=gamma=0.0;

  Trec=targetZ = targetMass = As =0.0;
  etag = ecut = 0.0;

  targetA = 0;

  cosTetMinNuc=0;
  cosTetMaxNuc=0;

  for(G4int i=0 ; i<5;  ++i){
    for(G4int j=0; j< 6; ++j){
      coeffb[i][j]=0;
    }
  }
  if(dangle[0] == 0.0) {
    for(G4int i=0; i<DIM; ++i){
      cross[i]=0;
    }
  }

  mottcoeff = new G4MottCoefficients();
}

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G4ScreeningMottCrossSection::~G4ScreeningMottCrossSection ( )

virtual

Definition at line 127 of file G4ScreeningMottCrossSection.cc.

{
  delete mottcoeff;
}

Member Function Documentation

G4double G4ScreeningMottCrossSection::AngleDistribution

(

G4double

)

G4double G4ScreeningMottCrossSection::FormFactor2ExpHof

(

G4double

angles

)

Definition at line 231 of file G4ScreeningMottCrossSection.cc.

{
  G4double M=targetMass;
  G4double E=tkinLab;
  G4double Etot=E+mass;
  G4double Tmax=2.*M*E*(E+2.*mass)/(mass*mass+M*M+2.*M*Etot);
  G4double T=Tmax*fG4pow->powN(sin(angles*0.5), 2);
  G4double q2=T*(T+2.*M);
  q2/=htc2;//1/cm2
  G4double RN=1.27e-13*G4Exp(G4Log(targetA)*0.27)*cm;
  G4double xN= (RN*RN*q2);
  G4double den=(1.+xN/12.);
  G4double FN=1./(den*den);
  G4double form2=(FN*FN);

  return form2;

  //cout<<"..................... form2 "<< form2<<endl;
}

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G4double G4ScreeningMottCrossSection::FormFactor2Gauss

(

G4double

angles

)

Definition at line 253 of file G4ScreeningMottCrossSection.cc.

{
  G4double M=targetMass;
  G4double E=tkinLab;
  G4double Etot=E+mass;
  G4double Tmax=2.*M*E*(E+2.*mass)/(mass*mass+M*M+2.*M*Etot);
  G4double T=Tmax*fG4pow->powN(sin(angles*0.5), 2);
  G4double q2=T*(T+2.*M);
  q2/=htc2;//1/cm2
  G4double RN=1.27e-13*G4Exp(G4Log(targetA)*0.27)*cm;
  G4double xN= (RN*RN*q2);

  G4double expo=(-xN/6.);
  G4double FN=G4Exp(expo);

  G4double form2=(FN*FN);

  return form2;

  //cout<<"..................... form2 "<< form2<<endl;
}

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G4double G4ScreeningMottCrossSection::FormFactor2UniformHelm

(

G4double

angles

)

Definition at line 277 of file G4ScreeningMottCrossSection.cc.

{
  G4double M=targetMass;
  G4double E=tkinLab;
  G4double Etot=E+mass;
  G4double Tmax=2.*M*E*(E+2.*mass)/(mass*mass+M*M+2.*M*Etot);
  G4double T=Tmax*fG4pow->powN(sin(angles*0.5), 2);
  G4double q2=T*(T+2.*M);
  q2=q2/(htc2*0.01);//1/cm2

  G4double q=G4Exp(G4Log(q2)*0.5);;
  G4double R0=1.2E-13*G4Exp(G4Log(targetA)/3.);
  G4double R1=2.0E-13;

  G4double x0=q*R0;
  G4double F0=(3./fG4pow->powN(x0,3))*(sin(x0)-x0*cos(x0));

  G4double x1=q*R1;
  G4double F1=(3./fG4pow->powN(x1,3))*(sin(x1)-x1*cos(x1));

  G4double F=F0*F1;

  G4double form2=(F*F);

  //cout<<"htc: "<<sqrt(htc2)<<" R0: "<<R0<<" F0: "<<F0<<" F1: "<<F1<<" Targer Mass: "<<targetMass<<" Energy: "<<tkinLab<<" ANGLE: "<<angles<<" FORM: "<<form2<<endl;

  return form2;

  //cout<<"..................... form2 "<< form2<<endl;
}

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G4double G4ScreeningMottCrossSection::GetMom2CM ( ) const

inline

Definition at line 194 of file G4ScreeningMottCrossSection.hh.

{
    return mom2;
}

G4double G4ScreeningMottCrossSection::GetMom2Lab ( ) const

inline

Definition at line 201 of file G4ScreeningMottCrossSection.hh.

{
        return momLab2;
}

G4ThreeVector G4ScreeningMottCrossSection::GetNewDirection

(

)

G4double G4ScreeningMottCrossSection::GetScatteringAngle

(

)

Definition at line 391 of file G4ScreeningMottCrossSection.cc.

{

  //cout<<"Z: "<<targetZ<<" Energy: "<<tkinLab/MeV<<endl;

  //    cout<<"................ tkinLab  "<< G4BestUnit(tkinLab,"Energy") << " anglemin=  "<<anglemin<<endl;
  //cout<<"anglemax=  "<<anglemax<<endl;
  //G4double r =3e-6*G4UniformRand();
  //G4double r=1e-12*G4UniformRand();
  G4double r=G4UniformRand();

  G4double scattangle=0;
  G4double y=0;
  G4double step=0;

  for(G4int i=DIM-1; i>=0; --i){
    step=(1./TotalCross)*cross[i];
    y+=step;
    if(r >=y-step && r<y ){
      scattangle= angle[i] +G4UniformRand()*dangle[i];
      break;
    }
  }
  //cout<<"Energy: "<<tkinLab/MeV<<" SCATTANGLE: "<<scattangle<<endl;
  return scattangle;
}

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G4double G4ScreeningMottCrossSection::GetScreeningAngle

(

)

Definition at line 160 of file G4ScreeningMottCrossSection.cc.

{
  SetScreeningCoefficient();

  G4double screenangle=2.*asin(sqrt(As));
  //    cout<<"  screenangle  "<<  screenangle <<endl;
  if(screenangle>=pi) screenangle=pi;

  return screenangle;
}

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G4double G4ScreeningMottCrossSection::GetScreeningCoefficient ( ) const

inline

Definition at line 216 of file G4ScreeningMottCrossSection.hh.

{
    return As;
}

G4double G4ScreeningMottCrossSection::GetTotalCross ( ) const

inline

Definition at line 224 of file G4ScreeningMottCrossSection.hh.

{
    return TotalCross;
}

G4double G4ScreeningMottCrossSection::GetTrec ( ) const

inline

Definition at line 209 of file G4ScreeningMottCrossSection.hh.

{
        return Trec;
}

void G4ScreeningMottCrossSection::Initialise	(	const G4ParticleDefinition *	p,
		G4double	cosThetaLim
	)

Definition at line 133 of file G4ScreeningMottCrossSection.cc.

{
  SetupParticle(p);
  tkin = targetZ = mom2 = 0.0;
  ecut = etag = DBL_MAX;
  particle = p;
  cosThetaMin = CosThetaLim;

}

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G4double G4ScreeningMottCrossSection::McFcorrection

(

G4double

angles

)

Definition at line 310 of file G4ScreeningMottCrossSection.cc.

{
  G4double  beta2=1./invbeta2;
  G4double sintmezzi=std::sin(angles/2.);
  G4double sin2tmezzi = sintmezzi*sintmezzi;
  G4double R=1.-beta2*sin2tmezzi + targetZ*alpha*beta*pi*sintmezzi*(1.-sintmezzi);
  return R;
}

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G4double G4ScreeningMottCrossSection::NuclearCrossSection

(

G4int

form

)

Definition at line 345 of file G4ScreeningMottCrossSection.cc.

{
  if(cosTetMaxNuc >= cosTetMinNuc) return 0.0;

  TotalCross=0;

  for(G4int i=0; i<DIM; ++i){
    G4double R=0;

    G4double F2=0;

    if(form==0){F2=1;}
    if(form==1){F2=FormFactor2ExpHof(tet[i]);}
    if(form==2){F2=FormFactor2Gauss(tet[i]);}
    if(form==3){F2=FormFactor2UniformHelm(tet[i]);}

    if (coeffb[0][0]!=0){
      //cout<<" Mott....targetZ "<< targetZ<<endl;
      R=RatioMottRutherford(tet[i]);
    } else if (coeffb[0][0]==0){
      // cout<<" McF.... targetZ "<< targetZ<<endl;
      R=McFcorrection(tet[i]);
    }

    //cout<<"----------------- R "<<R<<" F2 "<<F2<<endl;
    //                cout<<"angle "<<tet[i] << " F2 "<<F2<<endl;

    G4double den=2.*As+2.*fG4pow->powN(sin(tet[i]*0.5),2);
    G4double func=1./(den*den);

    G4double fatt= targetZ/(mu_rel*gamma*beta*beta);
    G4double sigma=e2*e2*fatt*fatt*func;
    G4double pi2sintet=twopi*sin(tet[i]);

    cross[i]=pi2sintet*F2*R*sigma*dangle[i];
    //cout<<i<<" Angle: "<<angle[i]<<" tet: "<<tet[i]<<" Cross: "<<cross[i]<<endl;
    if(cross[i]<0){cross[i]=0;};
    TotalCross+=cross[i];
  }//end integral

  //cout<< "ok ......... TotalCross "<<TotalCross<<endl;
  return TotalCross;
}

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G4double G4ScreeningMottCrossSection::RatioMottRutherford

(

G4double

angles

)

Definition at line 319 of file G4ScreeningMottCrossSection.cc.

{
  G4double R=0;
  G4double fcost=std::sqrt((1. -cos(angles)));
  G4double a[5];
  static const G4double shift=0.7181228;
  G4double beta0= beta -shift;

  for(G4int j=0 ;j<=4;j++){
    a[j]=0;
  }

  for(G4int j=0 ;j<=4;j++){
    for(G4int k=0;k<=5;k++ ){
      a[j]+=coeffb[j][k]*fG4pow->powN(beta0,k);
    }
  }

  for(G4int j=0; j<=4; ++j){
    R+=a[j]*fG4pow->powN(fcost,j);
  }
  return R;
}

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void G4ScreeningMottCrossSection::SetScreeningCoefficient

(

)

Definition at line 144 of file G4ScreeningMottCrossSection.cc.

{
  G4double alpha2=alpha*alpha;
  //Bohr radius
  G4double a0=  Bohr_radius  ;//0.529e-8*cm;
  //Thomas-Fermi screening length
  G4double aU=0.88534*a0/fG4pow->Z13(targetZ);
  G4double twoR2=aU*aU;

  G4double factor= 1.13 + 3.76*targetZ*targetZ*invbeta2*alpha2;
  As=0.25*(htc2)/(twoR2*mom2)*factor;
  //cout<<"0k .........................As  "<<As<<endl;
}

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void G4ScreeningMottCrossSection::SetupKinematic	(	G4double	kinEnergy,
		G4double	Z
	)

Definition at line 172 of file G4ScreeningMottCrossSection.cc.

{
  //...Target
  G4int iz = G4lrint(Z);
  G4double A = fNistManager->GetAtomicMassAmu(iz);
  G4int ia = G4lrint(A);
  G4double mass2 = G4NucleiProperties::GetNuclearMass(ia, iz);

  targetZ = Z;
  targetA = fNistManager->GetAtomicMassAmu(iz);
  targetMass= mass2;

  mottcoeff->SetMottCoeff(targetZ, coeffb);

  //cout<<"......... targetA "<< targetA <<endl;
  //cout<<"......... targetMass "<< targetMass/MeV <<endl;

  // incident particle lab
  tkinLab = ekin;
  momLab2 = tkinLab*(tkinLab + 2.0*mass);
  invbetaLab2 = 1.0 +  mass*mass/momLab2;

  G4double etot = tkinLab + mass;
  G4double ptot = sqrt(momLab2);
  G4double m12  = mass*mass;

  // relativistic reduced mass from publucation
  // A.P. Martynenko, R.N. Faustov, Teoret. mat. Fiz. 64 (1985) 179

  //incident particle & target nucleus
  G4double Ecm=sqrt(m12 + mass2*mass2 + 2.0*etot*mass2);
  mu_rel=mass*mass2/Ecm;
  G4double momCM= ptot*mass2/Ecm;
  // relative system
  mom2 = momCM*momCM;
  G4double x = mu_rel*mu_rel/mom2;
  invbeta2 = 1.0 + x;
  tkin = momCM*sqrt(invbeta2) - mu_rel;//Ekin of mu_rel
  G4double  beta2=1./invbeta2;
  beta=std::sqrt(beta2) ;
  G4double gamma2= invbeta2/x; 
  gamma=std::sqrt(gamma2);

  //.........................................................

  SetScreeningCoefficient();

  //Integration Angles definition

  cosTetMinNuc =cosThetaMin;
  cosTetMaxNuc =cosThetaMax;

  for(G4int i=0; i<DIM;  ++i ){
    cross[i]=0;
  }
}

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void G4ScreeningMottCrossSection::SetupParticle ( const G4ParticleDefinition *  p )

inline

Definition at line 183 of file G4ScreeningMottCrossSection.hh.

{
    particle = p;
    mass = particle->GetPDGMass();
    spin = particle->GetPDGSpin();
    if(0.0 != spin) { spin = 0.5; }
    tkin = 0.0;
}

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---

The documentation for this class was generated from the following files:

• geant4.10.03.p01/source/processes/electromagnetic/standard/include/G4ScreeningMottCrossSection.hh
• geant4.10.03.p01/source/processes/electromagnetic/standard/src/G4ScreeningMottCrossSection.cc