1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // |
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28 | // CERN Geneva Switzerland |
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29 | // |
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30 | // ------------ G4ReactionDynamics::TwoBody ------ |
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31 | // new method TwoBodyScattering |
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32 | // by Christian V"olcker (CERN-Munich), September 1997 |
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33 | // E-mail: Christian.Volcker@cern.ch |
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34 | // ************************************************************ |
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35 | //----------------------------------------------------------------------------- |
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36 | |
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37 | #include "G4ReactionKinematics.hh" |
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38 | |
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39 | // ************************************************************ |
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40 | void G4ReactionKinematics::TwoBodyScattering( |
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41 | const G4DynamicParticle* pIn1, const G4DynamicParticle* pIn2, |
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42 | G4DynamicParticle* pOut1, G4DynamicParticle* pOut2) |
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43 | // ************************************************************ |
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44 | { |
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45 | // initial particles: |
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46 | |
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47 | // - total invariant mass |
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48 | G4LorentzVector sumIn(pIn1->Get4Momentum()+pIn2->Get4Momentum()); |
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49 | G4double invariantMass=sumIn.mag(); |
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50 | |
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51 | // - beta of center-of-mass system |
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52 | G4ThreeVector betaCMS=sumIn.boostVector(); |
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53 | |
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54 | // final particles: |
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55 | |
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56 | // - get final particle masses |
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57 | G4double massOut1=pOut1->GetMass(); |
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58 | G4double massOut2=pOut2->GetMass(); |
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59 | |
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60 | // - calculate breakup momentum: |
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61 | G4double breakupMomentum=BreakupMomentum(invariantMass, massOut1, massOut2); |
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62 | |
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63 | // - isotropic decay angle |
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64 | G4double costheta = 2.0*G4UniformRand() - 1.0; |
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65 | G4double sintheta = std::sqrt(1.0 - costheta*costheta); |
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66 | G4double phi = 2.0*pi*G4UniformRand(); |
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67 | |
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68 | // - setup LorentzVectors |
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69 | G4double pz=costheta*breakupMomentum; |
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70 | G4double px=sintheta*std::cos(phi)*breakupMomentum; |
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71 | G4double py=sintheta*std::sin(phi)*breakupMomentum; |
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72 | |
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73 | G4double breakupMomentumSquared=breakupMomentum*breakupMomentum; |
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74 | G4double energy1=std::sqrt(breakupMomentumSquared+massOut1*massOut1); |
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75 | G4double energy2=std::sqrt(breakupMomentumSquared+massOut2*massOut2); |
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76 | |
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77 | G4LorentzVector lorentz1(px, py, pz, energy1); |
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78 | G4LorentzVector lorentz2(px, py, pz, energy2); |
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79 | |
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80 | // - back into lab system |
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81 | |
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82 | lorentz1.boost(betaCMS); |
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83 | lorentz2.boost(betaCMS); |
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84 | |
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85 | // fill in new particles: |
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86 | |
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87 | pOut1->Set4Momentum(lorentz1); |
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88 | pOut2->Set4Momentum(lorentz2); |
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89 | |
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90 | return; |
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91 | } |
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