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25 //
26 //
27 // FermiBreakUp de-excitation model
28 // by V. Ivanchenko (July 2016)
29 //
30
31 #include "G4FermiBreakUpUtil.hh"
32 #include "G4FermiFragment.hh"
33 #include "G4NuclearRadii.hh"
34 #include "G4PhysicalConstants.hh"
35
36 namespace G4FermiBreakUpUtil {
37
38 const G4double coeff = 0.6;
39
40 // Coulomb barrier
41 G4double CoulombBarrier(const G4int Z1, const G4int A1,
42 const G4int Z2, const G4int A2, const G4double exc) {
43 const G4double r1 = G4NuclearRadii::RadiusCB(Z1, A1);
44 const G4double r2 = G4NuclearRadii::RadiusCB(Z2, A2);
45 G4double CB = CLHEP::elm_coupling*(Z1*Z2)/(coeff*r1 + r2);
46 if (exc > 0.0) { CB /= (1.0 + std::sqrt(exc/((2*(A1 + A2))*CLHEP::MeV))); }
47 return CB;
48 }
49
50 // 2-body decay probability
51 G4double Probability(const G4int A,
52 const G4FermiFragment* f1, const G4FermiFragment* f2,
53 const G4double mass, const G4double exc) {
54 G4double prob = 0.0;
55 const G4double mass1 = f1->GetTotalEnergy();
56 const G4double mass2 = f2->GetTotalEnergy();
57 const G4double bCouloumb =
58 CoulombBarrier(f1->GetZ(), f1->GetA(), f2->GetZ(), f2->GetA(), exc);
59 if (mass < mass1 + mass2 + bCouloumb)
60 return prob;
61
62 // free energy
63 const G4double e = mass - mass1 - mass2;
64
65 // Spin factor S_n
66 const G4int S_n = (std::abs(f1->TwoSpinParity())+1)
67 *(std::abs(f2->TwoSpinParity())+1);
68
69 // mass factors
70 const G4double x = mass1*mass2/(mass1 + mass2);
71 G4double massFactor = x*std::sqrt(x);
72
73 // Permutation Factor G_n - search for identical fragments
74 G4double G_n = (f1 == f2) ? 0.5 : 1.0;
75
76 prob = (A*S_n) * massFactor*G_n*std::sqrt(e);
77 //G4cout << "prob= " << prob << " Coeff= " << Coeff << G4endl;
78 return prob;
79 }
80
81 G4bool CheckSpinParity(const G4FermiFragment* f1, const G4FermiFragment* f2,
82 const G4FermiFragment* f3)
83 {
84 // check parity
85 G4int spin1 = f1->TwoSpinParity();
86 G4int spin2 = f2->TwoSpinParity();
87 G4int spin3 = f3->TwoSpinParity();
88 if ((spin3 > 0 && spin1*spin2 < 0) || (spin3 < 0 && spin1*spin2 > 0))
89 return false;
90
91 return true;
92 }
93 }
94