G4FermiMomentum.hh

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00028 #ifndef G4FermiMomentum_h
00029 #define G4FermiMomentum_h 1
00030 
00031 #include "globals.hh"
00032 #include "G4ThreeVector.hh"
00033 #include "Randomize.hh"
00034 
00035 class G4FermiMomentum 
00036 {
00037 
00038   public:
00039     G4FermiMomentum();
00040     ~G4FermiMomentum();
00041     
00042     inline void Init(G4int anA, G4int aZ) {theA = anA; theZ = aZ;}
00043     
00044     inline G4double GetFermiMomentum(G4double density)
00045     {
00046         return constofpmax * cbrt(density * theA);
00047     }
00048     
00049     inline G4ThreeVector GetMomentum(G4double density, 
00050                                      G4double maxMomentum=-1.)
00051     { 
00052         if (maxMomentum < 0 ) maxMomentum=GetFermiMomentum(density);
00053         G4ThreeVector p;
00054         
00055         do {
00056             p=G4ThreeVector(2.*G4UniformRand()-1.,
00057                             2.*G4UniformRand()-1.,
00058                             2.*G4UniformRand()-1.);
00059             } while ( p.mag() > 1. );
00060         return p*maxMomentum; 
00061      }
00062 
00063   private:
00064 
00065     G4double cbrt(G4double x) { return std::pow(x,1./3.); }
00066 
00067   private:
00068   
00069     G4int theA;
00070     G4int theZ;
00071       // pmax= hbar * c * ( 3* pi**2 * rho )**(1/3) =
00072       //       hbar * c * ( 3* pi**2 )**(1/3) * rho**(1/3)=
00073       //       constofpmax * rho**(1/3)
00074     G4double constofpmax;
00075   
00076 };
00077 
00078 #endif
00079 

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