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G4KM_NucleonEqRhs.cc
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26 //
27 // -------------------------------------------------------------------
28 // GEANT 4 class implementation file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4KM_NucleonEqRhs.cc
33 //
34 // Author: Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
35 //
36 // Creation date: 5 June 2000
37 // -------------------------------------------------------------------
38 
39 #include "G4KM_NucleonEqRhs.hh"
40 #include "G4VNuclearDensity.hh"
41 
42 #include "G4PhysicalConstants.hh"
43 #include "G4Pow.hh"
44 
45 G4KM_NucleonEqRhs::G4KM_NucleonEqRhs(G4KM_DummyField *field,
46  G4V3DNucleus * nucleus) :
47  G4Mag_EqRhs(field), theNucleus(nucleus)
48 {
49  theMass = 0.;
50  A = theNucleus->GetMassNumber();
51  factor = hbarc*hbarc*G4Pow::GetInstance()->A23(3.*pi2*A)/3.;
52 }
53 
54 
55 void G4KM_NucleonEqRhs::EvaluateRhsGivenB(const G4double y[],
56  const G4double *,
57  G4double dydx[]) const
58 {
59  G4double yMod = std::sqrt(y[0]*y[0]+y[1]*y[1]+y[2]*y[2]);
60  G4double e = std::sqrt(theMass*theMass+y[3]*y[3]+y[4]*y[4]+y[5]*y[5]);
61 
62 // y[0..2] is position
63 // y[3..5] is momentum (and not mom.direction)
64 
65  dydx[0] = c_light*y[3]/e; //
66  dydx[1] = c_light*y[4]/e; // dq/dt=dH/dp = c*p/e
67  dydx[2] = c_light*y[5]/e; //
68 
69 /*
70  * // debug
71  * G4cout << " Nucleon RHS : 0..2(dpos/dt) " <<
72  * dydx[0] << " " <<
73  * dydx[1] << " " <<
74  * dydx[2] << " " << G4endl;
75  */
76 
77 
78 // V=K*rho(r) ==> dydx[3] = -dV/dr*dr/dx = -K*d(rho)/dr*dr/dx.
79 // GF should be V=K*rho(r) ==> dydx[3] = -dV/dr*dr/dx = -K*d(rho)/dr*dr/dt
80 // GF and dV/dt = dE/dt ==> dp/dt = dE/dt * dp/dE = dE/dt *e/p
81 // Idem for dydx[4] and dydx[5]
82 
83  G4ThreeVector pos(y[0],y[1],y[2]);
84 
85  const G4VNuclearDensity * nuclearDensity=theNucleus->GetNuclearDensity();
86 
87 // do not check for theMass != 0 : it is an error and core dump will signal it
88 
89  G4double density= nuclearDensity->GetDensity(pos);
90  G4double deriv(0);
91  if (density > 0 ) deriv = (factor/theMass)/
92  G4Pow::GetInstance()->A13(density)*nuclearDensity->GetDeriv(pos);
93 
94 // dydx[3] = yMod == 0 ? 0 : -deriv*y[0]/yMod;
95 // dydx[4] = yMod == 0 ? 0 : -deriv*y[1]/yMod;
96 // dydx[5] = yMod == 0 ? 0 : -deriv*y[2]/yMod;
97  dydx[3] = yMod == 0 ? 0 : deriv*y[0]/yMod*c_light;
98  dydx[4] = yMod == 0 ? 0 : deriv*y[1]/yMod*c_light;
99  dydx[5] = yMod == 0 ? 0 : deriv*y[2]/yMod*c_light;
100 
101 
102 /*
103  * // debug
104  * G4cout << " Nucleon RHS : 3..5(dE/dt) " <<
105  * dydx[3] << " " <<
106  * dydx[4] << " " <<
107  * dydx[5] << " " << G4endl;
108  */
109 }
110 
111 // Here by design, but it is unnecessary for nuclear fields
112 void G4KM_NucleonEqRhs::SetChargeMomentumMass(G4ChargeState,G4double ,G4double )
113 {
114 }