Geant4  10.00.p02
G4EqGravityField.cc
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25 //
26 //
27 // This is the right-hand side for equation of motion for a
28 // massive particle in a gravitational field.
29 //
30 // History:
31 // - 14.06.11 P.Gumplinger, Created.
32 // -------------------------------------------------------------------
33 // Adopted from G4EqMagElectricField.hh
34 //
35 // Thanks to Peter Fierlinger (PSI) and
36 // A. Capra and A. Fontana (INFN Pavia)
37 // -------------------------------------------------------------------
38 
39 #include "G4EqGravityField.hh"
40 #include "globals.hh"
41 #include "G4PhysicalConstants.hh"
42 
43 void
45  G4double,
46  G4double particleMass )
47 {
48  fMass = particleMass;
49 }
50 
51 void
53  const G4double G[],
54  G4double dydx[] ) const
55 {
56 
57  // Components of y:
58  // 0-2 dr/ds,
59  // 3-5 dp/ds - momentum derivatives
60 
61  G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
62  G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
63 
64  G4double Energy = std::sqrt(momentum_mag_square + fMass*fMass);
65  G4double cof2 = Energy/c_light;
66  G4double cof1 = inv_momentum_magnitude*fMass;
67  G4double inverse_velocity = Energy*inv_momentum_magnitude/c_light;
68 
69  dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
70  dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
71  dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
72 
73  dydx[3] = G[0]*cof1*cof2/c_light;
74  dydx[4] = G[1]*cof1*cof2/c_light; // m*g
75  dydx[5] = G[2]*cof1*cof2/c_light;
76 
77  // Lab Time of flight
78  dydx[7] = inverse_velocity;
79 
80  return;
81 }
void SetChargeMomentumMass(G4ChargeState particleCharge, G4double MomentumXc, G4double mass)
void EvaluateRhsGivenB(const G4double y[], const G4double Field[], G4double dydx[]) const
double G4double
Definition: G4Types.hh:76