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25 //
26 // G4MuonDecayChannelWithSpin
27 //
28 // Class decription:
29 //
30 // This class describes muon decay kinematics.
31 // It assumes V-A coupling with 1st order radiative corrections, the
32 // standard model parameter values, but gives incorrect energy spectrum
33 // for neutrinos.
34 // References:
35 // - Florian Scheck "Muon Physics", in Physics Reports
36 // (Review Section of Physics Letters) 44, No. 4 (1978)
37 // 187-248. North-Holland Publishing Company, Amsterdam at page 210 cc.
38 // - W.E. Fisher and F. Scheck, Nucl. Phys. B83 (1974) 25.
39
40 // Authors: P.Gumplinger and T.MacPhail, 17 August 2004
41 // --------------------------------------------------------------------
42 #ifndef G4MuonDecayChannelWithSpin_hh
43 #define G4MuonDecayChannelWithSpin_hh 1
44
45 #include "G4MuonDecayChannel.hh"
46 #include "G4ThreeVector.hh"
47 #include "globals.hh"
48
49 #include <CLHEP/Units/PhysicalConstants.h>
50
51 class G4MuonDecayChannelWithSpin : public G4MuonDecayChannel
52 {
53 public:
54 G4MuonDecayChannelWithSpin(const G4String& theParentName, G4double theBR);
55 ~G4MuonDecayChannelWithSpin() override = default;
56
57 G4DecayProducts* DecayIt(G4double) override;
58
59 protected:
60 // Copy constructor and assignment operator
61 G4MuonDecayChannelWithSpin(const G4MuonDecayChannelWithSpin&) = default;
62 G4MuonDecayChannelWithSpin& operator=(const G4MuonDecayChannelWithSpin&);
63
64 private:
65 G4MuonDecayChannelWithSpin() = default;
66
67 // Radiative Correction Factors
68 inline G4double F_c(G4double x, G4double x0, G4double omega);
69 inline G4double F_theta(G4double x, G4double x0, G4double omega);
70 G4double R_c(G4double x, G4double omega);
71 };
72
73 // ------------------------
74 // Inline methods
75 // ------------------------
76
77 inline G4double G4MuonDecayChannelWithSpin::F_c(G4double x, G4double x0, G4double omega)
78 {
79 G4double f_c;
80
81 f_c = (5. + 17. * x - 34. * x * x) * (omega + std::log(x)) - 22. * x + 34. * x * x;
82 f_c = (1. - x) / (3. * x * x) * f_c;
83 f_c = (6. - 4. * x) * R_c(x, omega) + (6. - 6. * x) * std::log(x) + f_c;
84 f_c = (CLHEP::fine_structure_const / CLHEP::twopi) * (x * x - x0 * x0) * f_c;
85
86 return f_c;
87 }
88
89 inline G4double G4MuonDecayChannelWithSpin::F_theta(G4double x, G4double x0, G4double omega)
90 {
91 G4double f_theta;
92
93 f_theta = (1. + x + 34 * x * x) * (omega + std::log(x)) + 3. - 7. * x - 32. * x * x;
94 f_theta = f_theta + ((4. * (1. - x) * (1. - x)) / x) * std::log(1. - x);
95 f_theta = (1. - x) / (3. * x * x) * f_theta;
96 f_theta = (2. - 4. * x) * R_c(x, omega) + (2. - 6. * x) * std::log(x) - f_theta;
97 f_theta = (CLHEP::fine_structure_const / CLHEP::twopi) * (x * x - x0 * x0) * f_theta;
98
99 return f_theta;
100 }
101
102 #endif
103