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25 // 25 //
26 // G4EqGravityField implementation <<
27 // 26 //
28 // This is the right-hand side for equation of << 27 // This is the right-hand side for equation of motion for a
29 // massive particle in a gravitational field. << 28 // massive particle in a gravitational field.
30 // 29 //
31 // Created: P.Gumplinger, 14.06.11 - Adopted f << 30 // History:
32 // Thanks to P.Fierlinger (PSI) and A << 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)
33 // ------------------------------------------- 37 // -------------------------------------------------------------------
34 38
35 #include "G4EqGravityField.hh" 39 #include "G4EqGravityField.hh"
36 #include "globals.hh" 40 #include "globals.hh"
37 #include "G4PhysicalConstants.hh" 41 #include "G4PhysicalConstants.hh"
38 42
39 G4EqGravityField::G4EqGravityField(G4UniformGr <<
40 : G4EquationOfMotion( gField ) <<
41 { <<
42 } <<
43 <<
44 G4EqGravityField::~G4EqGravityField() = defaul <<
45 <<
46 void 43 void
47 G4EqGravityField::SetChargeMomentumMass(G4Char << 44 G4EqGravityField::SetChargeMomentumMass(G4double,
48 G4doub 45 G4double,
49 G4doub 46 G4double particleMass )
50 { 47 {
51 fMass = particleMass; 48 fMass = particleMass;
52 } 49 }
53 50
54 void 51 void
55 G4EqGravityField::EvaluateRhsGivenB(const G4do 52 G4EqGravityField::EvaluateRhsGivenB(const G4double y[],
56 const G4do 53 const G4double G[],
57 G4do << 54 G4double dydx[] ) const
58 { 55 {
59 56
60 // Components of y: 57 // Components of y:
61 // 0-2 dr/ds, 58 // 0-2 dr/ds,
62 // 3-5 dp/ds - momentum derivatives 59 // 3-5 dp/ds - momentum derivatives
63 60
64 G4double momentum_mag_square = y[3]*y[3] + y 61 G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
65 G4double inv_momentum_magnitude = 1.0 / std: 62 G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
66 63
67 G4double Energy = std::sqrt(momentum_mag_squ 64 G4double Energy = std::sqrt(momentum_mag_square + fMass*fMass);
68 G4double cof2 = Energy/c_light; 65 G4double cof2 = Energy/c_light;
69 G4double cof1 = inv_momentum_magnitude*fMass 66 G4double cof1 = inv_momentum_magnitude*fMass;
70 G4double inverse_velocity = Energy*inv_momen 67 G4double inverse_velocity = Energy*inv_momentum_magnitude/c_light;
71 68
72 dydx[0] = y[3]*inv_momentum_magnitude; 69 dydx[0] = y[3]*inv_momentum_magnitude; // (d/ds)x = Vx/V
73 dydx[1] = y[4]*inv_momentum_magnitude; 70 dydx[1] = y[4]*inv_momentum_magnitude; // (d/ds)y = Vy/V
74 dydx[2] = y[5]*inv_momentum_magnitude; 71 dydx[2] = y[5]*inv_momentum_magnitude; // (d/ds)z = Vz/V
75 72
76 dydx[3] = G[0]*cof1*cof2/c_light; << 73 dydx[3] = G[0]*cof1*cof2;
77 dydx[4] = G[1]*cof1*cof2/c_light; << 74 dydx[4] = G[1]*cof1*cof2; // m*g
78 dydx[5] = G[2]*cof1*cof2/c_light; << 75 dydx[5] = G[2]*cof1*cof2;
79 76
80 // Lab Time of flight 77 // Lab Time of flight
81 // <<
82 dydx[7] = inverse_velocity; 78 dydx[7] = inverse_velocity;
83 79
84 return; 80 return;
85 } 81 }
86 82