00001 // 00002 // ******************************************************************** 00003 // * License and Disclaimer * 00004 // * * 00005 // * The Geant4 software is copyright of the Copyright Holders of * 00006 // * the Geant4 Collaboration. It is provided under the terms and * 00007 // * conditions of the Geant4 Software License, included in the file * 00008 // * LICENSE and available at http://cern.ch/geant4/license . These * 00009 // * include a list of copyright holders. * 00010 // * * 00011 // * Neither the authors of this software system, nor their employing * 00012 // * institutes,nor the agencies providing financial support for this * 00013 // * work make any representation or warranty, express or implied, * 00014 // * regarding this software system or assume any liability for its * 00015 // * use. Please see the license in the file LICENSE and URL above * 00016 // * for the full disclaimer and the limitation of liability. * 00017 // * * 00018 // * This code implementation is the result of the scientific and * 00019 // * technical work of the GEANT4 collaboration. * 00020 // * By using, copying, modifying or distributing the software (or * 00021 // * any work based on the software) you agree to acknowledge its * 00022 // * use in resulting scientific publications, and indicate your * 00023 // * acceptance of all terms of the Geant4 Software license. * 00024 // ******************************************************************** 00025 // 00026 // 00027 // 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