Geant4 Cross Reference |
1 // 1 2 // ******************************************* 3 // * License and Disclaimer 4 // * 5 // * The Geant4 software is copyright of th 6 // * the Geant4 Collaboration. It is provided 7 // * conditions of the Geant4 Software License 8 // * LICENSE and available at http://cern.ch/ 9 // * include a list of copyright holders. 10 // * 11 // * Neither the authors of this software syst 12 // * institutes,nor the agencies providing fin 13 // * work make any representation or warran 14 // * regarding this software system or assum 15 // * use. Please see the license in the file 16 // * for the full disclaimer and the limitatio 17 // * 18 // * This code implementation is the result 19 // * technical work of the GEANT4 collaboratio 20 // * By using, copying, modifying or distri 21 // * any work based on the software) you ag 22 // * use in resulting scientific publicati 23 // * acceptance of all terms of the Geant4 Sof 24 // ******************************************* 25 // 26 // 27 // Multibody "phase space" generator using Kop 28 // 29 // Author: Michael Kelsey (SLAC) <kelsey@slac 30 31 #include "G4HadPhaseSpaceKopylov.hh" 32 #include "G4LorentzVector.hh" 33 #include "G4Pow.hh" 34 #include "Randomize.hh" 35 #include <vector> 36 #include <algorithm> 37 #include <numeric> 38 #include <cmath> 39 40 41 // Generator 42 43 void G4HadPhaseSpaceKopylov:: 44 GenerateMultiBody(G4double initialMass, 45 const std::vector<G4double>& masses, 46 std::vector<G4LorentzVector>& finalState 47 if (GetVerboseLevel()) G4cout << GetName() < 48 49 finalState.clear(); 50 51 G4int N = (G4int)masses.size(); 52 finalState.resize(N); 53 54 G4double mtot = std::accumulate(masses.begin 55 G4double mu = mtot; 56 G4double PFragMagCM = 0.0; 57 G4double Mass = initialMass; 58 G4double T = Mass-mtot; 59 G4LorentzVector PFragCM(0.0,0.0,0.0,0.0); 60 G4LorentzVector PRestCM(0.0,0.0,0.0,0.0); 61 G4LorentzVector PRestLab(0.0,0.0,0.0,Mass); 62 63 for (G4int k=N-1; k>0; --k) { 64 mu -= masses[k]; 65 T *= (k>1) ? BetaKopylov(k) : 0.; 66 67 G4double RestMass = mu + T; 68 69 PFragMagCM = TwoBodyMomentum(Mass,masses[k 70 71 // Create a unit vector with a random dire 72 G4ThreeVector RandVector = UniformVector(P 73 74 PFragCM.setVectM(RandVector,masses[k]); 75 PRestCM.setVectM(-RandVector,RestMass); 76 77 G4ThreeVector BoostV = PRestLab.boostVecto 78 79 PFragCM.boost(BoostV); 80 PRestCM.boost(BoostV); 81 PRestLab = PRestCM; 82 Mass = RestMass; 83 finalState[k] = PFragCM; 84 } 85 86 finalState[0] = PRestLab; 87 } 88 89 90 // Generate scale factor for final state parti 91 92 G4double G4HadPhaseSpaceKopylov::BetaKopylov(G 93 G4Pow* g4pow = G4Pow::GetInstance(); 94 95 G4int N = 3*K - 5; 96 G4double xN = G4double(N); 97 G4double Fmax = std::sqrt(g4pow->powN(xN/(xN 98 99 G4double F, chi; 100 const G4int maxNumberOfLoops = 10000; 101 G4int loopCounter = 0; 102 do { 103 chi = G4UniformRand(); 104 F = std::sqrt(g4pow->powN(chi,N)*(1.-chi)) 105 } while ( ( Fmax*G4UniformRand() > F ) && ++ 106 if ( loopCounter >= maxNumberOfLoops ) { 107 G4ExceptionDescription ed; 108 ed << " Failed sampling after maxNumberOfL 109 G4Exception( " G4HadPhaseSpaceKopylov::Bet 110 } 111 112 return chi; 113 } 114