| 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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