[819] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 4 | // * * |
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| 10 | // * * |
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| 11 | // * Neither the authors of this software system, nor their employing * |
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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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| 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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| 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 | // $Id: G4SingleDiffractiveExcitation.cc,v 1.1 2007/05/25 07:30:47 gunter Exp $ |
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| 28 | // ------------------------------------------------------------ |
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| 29 | // GEANT 4 class implemetation file |
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| 30 | // |
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| 31 | // ---------------- G4SingleDiffractiveExcitation -------------- |
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| 32 | // by Gunter Folger, October 1998. |
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| 33 | // diffractive Excitation used by strings models |
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| 34 | // Take a projectile and a target |
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| 35 | // excite the projectile and target |
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| 36 | // ------------------------------------------------------------ |
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| 37 | |
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| 38 | |
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| 39 | #include "globals.hh" |
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| 40 | #include "Randomize.hh" |
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| 41 | |
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| 42 | #include "G4SingleDiffractiveExcitation.hh" |
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| 43 | #include "G4LorentzRotation.hh" |
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| 44 | #include "G4ThreeVector.hh" |
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| 45 | #include "G4ParticleDefinition.hh" |
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| 46 | #include "G4VSplitableHadron.hh" |
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| 47 | #include "G4ExcitedString.hh" |
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| 48 | //#include "G4ios.hh" |
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| 49 | |
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| 50 | G4SingleDiffractiveExcitation::G4SingleDiffractiveExcitation(G4double sigmaPt, G4double minextraMass,G4double x0mass) |
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| 51 | : |
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| 52 | widthOfPtSquare(-2*sqr(sigmaPt)) , minExtraMass(minextraMass), |
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| 53 | minmass(x0mass) |
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| 54 | { |
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| 55 | } |
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| 56 | |
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| 57 | G4bool G4SingleDiffractiveExcitation:: |
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| 58 | ExciteParticipants(G4VSplitableHadron *projectile, G4VSplitableHadron *target) const |
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| 59 | { |
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| 60 | |
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| 61 | G4LorentzVector Pprojectile=projectile->Get4Momentum(); |
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| 62 | G4double Mprojectile2=sqr(projectile->GetDefinition()->GetPDGMass() + minExtraMass); |
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| 63 | |
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| 64 | G4LorentzVector Ptarget=target->Get4Momentum(); |
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| 65 | G4double Mtarget2=sqr(target->GetDefinition()->GetPDGMass() + minExtraMass); |
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| 66 | // G4cout << "E proj, target :" << Pprojectile.e() << ", " << |
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| 67 | // Ptarget.e() << G4endl; |
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| 68 | |
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| 69 | G4bool KeepProjectile= G4UniformRand() > 0.5; |
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| 70 | |
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| 71 | // reset the min.mass of the non diffractive particle to its value, ( minus a bit for rounding...) |
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| 72 | if ( KeepProjectile ) |
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| 73 | { |
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| 74 | // cout << " Projectile fix" << G4endl; |
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| 75 | Mprojectile2 = sqr(projectile->GetDefinition()->GetPDGMass() * (1-perCent) ); |
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| 76 | } else { |
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| 77 | // cout << " Target fix" << G4endl; |
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| 78 | Mtarget2=sqr(target->GetDefinition()->GetPDGMass() * (1-perCent) ); |
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| 79 | } |
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| 80 | |
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| 81 | // Transform momenta to cms and then rotate parallel to z axis; |
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| 82 | |
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| 83 | G4LorentzVector Psum; |
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| 84 | Psum=Pprojectile+Ptarget; |
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| 85 | |
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| 86 | G4LorentzRotation toCms(-1*Psum.boostVector()); |
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| 87 | |
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| 88 | G4LorentzVector Ptmp=toCms*Pprojectile; |
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| 89 | |
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| 90 | if ( Ptmp.pz() <= 0. ) |
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| 91 | { |
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| 92 | // "String" moving backwards in CMS, abort collision !! |
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| 93 | // G4cout << " abort Collision!! " << G4endl; |
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| 94 | return false; |
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| 95 | } |
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| 96 | |
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| 97 | toCms.rotateZ(-1*Ptmp.phi()); |
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| 98 | toCms.rotateY(-1*Ptmp.theta()); |
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| 99 | |
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| 100 | // G4cout << "Pprojectile be4 boost " << Pprojectile << G4endl; |
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| 101 | // G4cout << "Ptarget be4 boost : " << Ptarget << G4endl; |
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| 102 | |
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| 103 | |
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| 104 | |
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| 105 | G4LorentzRotation toLab(toCms.inverse()); |
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| 106 | |
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| 107 | Pprojectile.transform(toCms); |
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| 108 | Ptarget.transform(toCms); |
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| 109 | |
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| 110 | G4LorentzVector Qmomentum; |
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| 111 | G4int whilecount=0; |
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| 112 | do { |
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| 113 | // Generate pt |
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| 114 | |
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| 115 | G4double maxPtSquare=sqr(Ptarget.pz()); |
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| 116 | if (whilecount++ >= 500 && (whilecount%100)==0) |
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| 117 | // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants possibly looping" |
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| 118 | // << ", loop count/ maxPtSquare : " |
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| 119 | // << whilecount << " / " << maxPtSquare << G4endl; |
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| 120 | if (whilecount > 1000 ) |
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| 121 | { |
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| 122 | Qmomentum=G4LorentzVector(0.,0.,0.,0.); |
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| 123 | // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants: Aborting loop!" << G4endl; |
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| 124 | return false; // Ignore this interaction |
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| 125 | } |
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| 126 | Qmomentum=G4LorentzVector(GaussianPt(widthOfPtSquare,maxPtSquare),0); |
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| 127 | |
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| 128 | |
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| 129 | // Momentum transfer |
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| 130 | G4double Xmin = minmass / ( Pprojectile.e() + Ptarget.e() ); |
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| 131 | G4double Xmax=1.; |
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| 132 | G4double Xplus =ChooseX(Xmin,Xmax); |
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| 133 | G4double Xminus=ChooseX(Xmin,Xmax); |
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| 134 | |
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| 135 | G4double pt2=G4ThreeVector(Qmomentum.vect()).mag2(); |
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| 136 | G4double Qplus =-1 * pt2 / Xminus/Ptarget.minus(); |
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| 137 | G4double Qminus= pt2 / Xplus /Pprojectile.plus(); |
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| 138 | |
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| 139 | if ( KeepProjectile ) |
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| 140 | { |
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| 141 | Qminus = (sqr(projectile->GetDefinition()->GetPDGMass()) + pt2 ) |
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| 142 | / (Pprojectile.plus() + Qplus ) |
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| 143 | - Pprojectile.minus(); |
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| 144 | } else |
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| 145 | { |
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| 146 | Qplus = Ptarget.plus() |
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| 147 | - (sqr(target->GetDefinition()->GetPDGMass()) + pt2 ) |
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| 148 | / (Ptarget.minus() - Qminus ); |
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| 149 | } |
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| 150 | |
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| 151 | Qmomentum.setPz( (Qplus-Qminus)/2 ); |
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| 152 | Qmomentum.setE( (Qplus+Qminus)/2 ); |
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| 153 | |
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| 154 | // G4cout << "Qplus / Qminus " << Qplus << " / " << Qminus<<G4endl; |
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| 155 | // G4cout << "pt2 " << pt2 << G4endl; |
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| 156 | // G4cout << "Qmomentum " << Qmomentum << G4endl; |
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| 157 | // G4cout << " Masses (P/T) : " << (Pprojectile+Qmomentum).mag() << |
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| 158 | // " / " << (Ptarget-Qmomentum).mag() << G4endl; |
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| 159 | |
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| 160 | } while ( (Ptarget-Qmomentum).mag2() <= Mtarget2 |
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| 161 | || (Pprojectile+Qmomentum).mag2() <= Mprojectile2 |
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| 162 | || (Ptarget-Qmomentum).e() < 0. |
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| 163 | || (Pprojectile+Qmomentum).e() < 0. ); |
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| 164 | |
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| 165 | |
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| 166 | // G4double Ecms=Pprojectile.e() + Ptarget.e(); |
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| 167 | |
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| 168 | Pprojectile += Qmomentum; |
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| 169 | |
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| 170 | Ptarget -= Qmomentum; |
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| 171 | |
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| 172 | // G4cout << "Pprojectile.e() : " << Pprojectile.e() << G4endl; |
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| 173 | // G4cout << "Ptarget.e() : " << Ptarget.e() << G4endl; |
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| 174 | |
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| 175 | // G4cout << "end event_______________________________________________"<<G4endl; |
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| 176 | // |
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| 177 | |
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| 178 | |
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| 179 | // G4cout << "Pprojectile with Q : " << Pprojectile << G4endl; |
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| 180 | // G4cout << "Ptarget with Q : " << Ptarget << G4endl; |
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| 181 | // G4cout << "Projectile back: " << toLab * Pprojectile << G4endl; |
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| 182 | // G4cout << "Target back: " << toLab * Ptarget << G4endl; |
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| 183 | |
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| 184 | // Transform back and update SplitableHadron Participant. |
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| 185 | Pprojectile.transform(toLab); |
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| 186 | Ptarget.transform(toLab); |
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| 187 | |
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| 188 | // G4cout << "G4SingleDiffractiveExcitation- Target mass " << Ptarget.mag() << G4endl; |
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| 189 | // G4cout << "G4SingleDiffractiveExcitation- Projectile mass " << Pprojectile.mag() << G4endl; |
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| 190 | |
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| 191 | target->Set4Momentum(Ptarget); |
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| 192 | projectile->Set4Momentum(Pprojectile); |
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| 193 | |
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| 194 | |
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| 195 | return true; |
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| 196 | } |
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| 197 | |
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| 198 | |
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| 199 | |
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| 200 | |
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| 201 | // --------- private methods ---------------------- |
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| 202 | |
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| 203 | G4double G4SingleDiffractiveExcitation::ChooseX(G4double Xmin, G4double Xmax) const |
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| 204 | { |
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| 205 | // choose an x between Xmin and Xmax with P(x) ~ 1/x |
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| 206 | |
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| 207 | // to be improved... |
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| 208 | |
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| 209 | G4double range=Xmax-Xmin; |
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| 210 | |
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| 211 | if ( Xmin <= 0. || range <=0. ) |
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| 212 | { |
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| 213 | G4cout << " Xmin, range : " << Xmin << " , " << range << G4endl; |
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| 214 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation::ChooseX : Invalid arguments "); |
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| 215 | } |
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| 216 | |
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| 217 | G4double x; |
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| 218 | do { |
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| 219 | x=Xmin + G4UniformRand() * range; |
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| 220 | } while ( Xmin/x < G4UniformRand() ); |
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| 221 | |
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| 222 | // cout << "DiffractiveX "<<x<<G4endl; |
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| 223 | return x; |
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| 224 | } |
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| 225 | |
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| 226 | G4ThreeVector G4SingleDiffractiveExcitation::GaussianPt(G4double widthSquare, G4double maxPtSquare) const |
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| 227 | { // @@ this method is used in FTFModel as well. Should go somewhere common! |
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| 228 | |
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| 229 | G4double pt2; |
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| 230 | |
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| 231 | do { |
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| 232 | pt2=widthSquare * std::log( G4UniformRand() ); |
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| 233 | } while ( pt2 > maxPtSquare); |
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| 234 | |
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| 235 | pt2=std::sqrt(pt2); |
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| 236 | |
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| 237 | G4double phi=G4UniformRand() * twopi; |
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| 238 | |
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| 239 | return G4ThreeVector (pt2*std::cos(phi), pt2*std::sin(phi), 0.); |
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| 240 | } |
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| 241 | |
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| 242 | G4SingleDiffractiveExcitation::G4SingleDiffractiveExcitation(const G4SingleDiffractiveExcitation &) |
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| 243 | : G4QGSDiffractiveExcitation(), |
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| 244 | widthOfPtSquare(0) , minExtraMass(0), |
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| 245 | minmass(0) |
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| 246 | { |
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| 247 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation copy contructor not meant to be called"); |
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| 248 | } |
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| 249 | |
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| 250 | |
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| 251 | G4SingleDiffractiveExcitation::~G4SingleDiffractiveExcitation() |
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| 252 | { |
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| 253 | } |
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| 254 | |
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| 255 | |
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| 256 | const G4SingleDiffractiveExcitation & G4SingleDiffractiveExcitation::operator=(const G4SingleDiffractiveExcitation &) |
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| 257 | { |
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| 258 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation = operator meant to be called"); |
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| 259 | return *this; |
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| 260 | } |
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| 261 | |
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| 262 | |
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| 263 | int G4SingleDiffractiveExcitation::operator==(const G4SingleDiffractiveExcitation &) const |
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| 264 | { |
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| 265 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation == operator meant to be called"); |
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| 266 | return false; |
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| 267 | } |
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| 268 | |
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| 269 | int G4SingleDiffractiveExcitation::operator!=(const G4SingleDiffractiveExcitation &) const |
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| 270 | { |
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| 271 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation != operator meant to be called"); |
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| 272 | return true; |
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| 273 | } |
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| 274 | |
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| 275 | |
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| 276 | |
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| 277 | |
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| 278 | |
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