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27 // -------------------------------------------------------------------
28 // GEANT 4 class implementation file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4KM_OpticalEqRhs.cc
33 //
34 // Author: Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
35 //
36 // Creation date: 5 June 2000
37 // -------------------------------------------------------------------
38
39 #include "G4KM_OpticalEqRhs.hh"
40 #include "G4PhysicalConstants.hh"
41 #include "G4NucleiProperties.hh"
42 #include "G4VNuclearDensity.hh"
43 #include "G4HadTmpUtil.hh"
44
45 G4KM_OpticalEqRhs::G4KM_OpticalEqRhs(G4KM_DummyField *field,
46 G4V3DNucleus * nucleus) :
47 G4Mag_EqRhs(field), theNucleus(nucleus)
48 {
49 theFactor = 0;
50 theMass = 0;
51 }
52
53
54 void G4KM_OpticalEqRhs::SetFactor(G4double mass, G4double opticalParameter)
55 {
56 G4double A = theNucleus->GetMassNumber();
57 G4double Z = theNucleus->GetCharge();
58 G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(G4lrint(A), G4lrint(Z));
59 G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
60 G4double reducedMass = mass*nucleusMass/(mass+nucleusMass);
61
62 G4double nucleonMass = (proton_mass_c2+neutron_mass_c2)/2;
63
64 // _factor in (MeV*fermi)*fermi/MeV = fermi*fermi -- need to have A as density normalized to 1
65 theFactor = 2*pi*hbarc*hbarc*(1+mass/nucleonMass)* opticalParameter/reducedMass * A;
66
67 theMass = mass;
68 }
69
70
71 void G4KM_OpticalEqRhs::EvaluateRhsGivenB(const G4double y[], const G4double *,
72 G4double dydx[]) const
73 {
74 G4double yMod = std::sqrt(y[0]*y[0]+y[1]*y[1]+y[2]*y[2]);
75 G4double e = std::sqrt(theMass*theMass+y[3]*y[3]+y[4]*y[4]+y[5]*y[5]);
76 dydx[0] = c_light*y[3]/e; //
77 dydx[1] = c_light*y[4]/e; // dq/dt=dH/dp = c*p/e
78 dydx[2] = c_light*y[5]/e; //
79
80 // V=K*rho(r) ==> dydx[3] = -dV/dr*dr/dx = -K*d(rho)/dr*dr/dx.
81 // Idem for dydx[4] and dydx[5]
82
83 const G4VNuclearDensity * nuclearDensity=theNucleus->GetNuclearDensity();
84
85 G4ThreeVector pos(y[0],y[1],y[2]);
86 G4double deriv = theFactor*nuclearDensity->GetDeriv(pos);
87
88 dydx[3] = yMod == 0 ? 0 : -deriv*y[0]/yMod*c_light;
89 dydx[4] = yMod == 0 ? 0 : -deriv*y[1]/yMod*c_light;
90 dydx[5] = yMod == 0 ? 0 : -deriv*y[2]/yMod*c_light;
91 }
92
93 // Here by design, but it is unnecessary for nuclear fields
94 void G4KM_OpticalEqRhs::SetChargeMomentumMass(G4ChargeState,G4double ,G4double )
95 {
96 }
97