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25 //
26 //
27 //
28
29 // ------------------------------------------------------------
30 // GEANT 4 class implemetation file
31 //
32 // ---------------- G4ElasticHNScattering --------------
33 // by V. Uzhinsky, March 2008.
34 // elastic scattering used by Fritiof model
35 // Take a projectile and a target
36 // scatter the projectile and target
37 // ---------------------------------------------------------------------
38
39 #include "globals.hh"
40 #include "Randomize.hh"
41 #include "G4PhysicalConstants.hh"
42 #include "G4SystemOfUnits.hh"
43
44 #include "G4ElasticHNScattering.hh"
45 #include "G4LorentzRotation.hh"
46 #include "G4ThreeVector.hh"
47 #include "G4ParticleDefinition.hh"
48 #include "G4VSplitableHadron.hh"
49 #include "G4ExcitedString.hh"
50 #include "G4FTFParameters.hh"
51
52 #include "G4SampleResonance.hh"
53
54 #include "G4Exp.hh"
55 #include "G4Log.hh"
56
57 //============================================================================
58
59 G4ElasticHNScattering::G4ElasticHNScattering() {}
60
61
62 //============================================================================
63
64 G4bool G4ElasticHNScattering::ElasticScattering( G4VSplitableHadron* projectile,
65 G4VSplitableHadron* target,
66 G4FTFParameters* theParameters ) const {
67 projectile->IncrementCollisionCount( 1 );
68 target->IncrementCollisionCount( 1 );
69
70 if ( projectile->Get4Momentum().z() < 0.0 ) return false; //Uzhi Aug.2019
71
72 // Projectile parameters
73 G4LorentzVector Pprojectile = projectile->Get4Momentum();
74 G4double M0projectile = Pprojectile.mag();
75 G4double M0projectile2 = M0projectile * M0projectile;
76
77 // Target parameters
78 G4LorentzVector Ptarget = target->Get4Momentum();
79 G4double M0target = Ptarget.mag();
80 G4double M0target2 = M0target * M0target;
81
82 G4double AveragePt2 = theParameters->GetAvaragePt2ofElasticScattering();
83
84 // Transform momenta to cms and then rotate parallel to z axis;
85 G4LorentzVector Psum;
86 Psum = Pprojectile + Ptarget;
87 G4LorentzRotation toCms( -1*Psum.boostVector() );
88 G4LorentzVector Ptmp = toCms*Pprojectile;
89 if ( Ptmp.pz() <= 0.0 ) return false;
90 //"String" moving backwards in CMS, abort collision !
91 //G4cout << " abort Collision! " << G4endl;
92 toCms.rotateZ( -1*Ptmp.phi() );
93 toCms.rotateY( -1*Ptmp.theta() );
94 G4LorentzRotation toLab( toCms.inverse() );
95 Pprojectile.transform( toCms );
96 Ptarget.transform( toCms );
97
98 G4double PZcms2, PZcms;
99 G4double S = Psum.mag2();
100 G4double SqrtS = std::sqrt( S );
101 if ( SqrtS < M0projectile + M0target ) return false;
102
103 PZcms2 = ( S*S + sqr( M0projectile2 ) + sqr( M0target2 )
104 - 2*S*M0projectile2 - 2*S*M0target2 - 2*M0projectile2*M0target2 ) / 4.0 / S;
105
106 PZcms = ( PZcms2 > 0.0 ? std::sqrt( PZcms2 ) : 0.0 );
107
108 G4double maxPtSquare = PZcms2;
109
110 // Now we can calculate the transferred Pt
111 G4double Pt2;
112 G4double ProjMassT2, ProjMassT;
113 G4double TargMassT2, TargMassT;
114 G4LorentzVector Qmomentum;
115
116 const G4int maxNumberOfLoops = 1000;
117 G4int loopCounter = 0;
118 do {
119 Qmomentum = G4LorentzVector( GaussianPt( AveragePt2, maxPtSquare ), 0.0 );
120 Pt2 = G4ThreeVector( Qmomentum.vect() ).mag2();
121 ProjMassT2 = M0projectile2 + Pt2;
122 ProjMassT = std::sqrt( ProjMassT2 );
123 TargMassT2 = M0target2 + Pt2;
124 TargMassT = std::sqrt( TargMassT2 );
125 } while ( ( SqrtS < ProjMassT + TargMassT ) &&
126 ++loopCounter < maxNumberOfLoops ); /* Loop checking, 10.08.2015, A.Ribon */
127 if ( loopCounter >= maxNumberOfLoops ) {
128 return false;
129 }
130
131 PZcms2 = ( S*S + sqr( ProjMassT2 ) + sqr( TargMassT2 )
132 - 2.0*S*ProjMassT2 - 2.0*S*TargMassT2 - 2.0*ProjMassT2*TargMassT2 ) / 4.0 / S;
133
134 if ( PZcms2 < 0.0 ) { PZcms2 = 0.0; }; // to avoid the exactness problem
135 PZcms = std::sqrt( PZcms2 );
136 Pprojectile.setPz( PZcms );
137 Ptarget.setPz( -PZcms );
138 Pprojectile += Qmomentum;
139 Ptarget -= Qmomentum;
140
141 // Transform back and update SplitableHadron Participant.
142 Pprojectile.transform( toLab );
143 Ptarget.transform( toLab );
144
145 // Calculation of the creation time
146 projectile->SetTimeOfCreation( target->GetTimeOfCreation() );
147 projectile->SetPosition( target->GetPosition() );
148
149 // Creation time and position of target nucleon were determined at
150 // ReggeonCascade() of G4FTFModel
151
152 projectile->Set4Momentum( Pprojectile );
153 target->Set4Momentum( Ptarget );
154
155 //projectile->IncrementCollisionCount( 1 );
156 //target->IncrementCollisionCount( 1 );
157
158 return true;
159 }
160
161
162 //============================================================================
163
164 G4ThreeVector G4ElasticHNScattering::GaussianPt( G4double AveragePt2,
165 G4double maxPtSquare ) const {
166 // @@ this method is used in FTFModel as well. Should go somewhere common!
167 G4double Pt2( 0.0 );
168 if ( AveragePt2 <= 0.0 ) {
169 Pt2 = 0.0;
170 } else {
171 Pt2 = -AveragePt2 * G4Log( 1.0 + G4UniformRand() * ( G4Exp( -maxPtSquare/AveragePt2 ) -1.0 ) );
172 }
173 G4double Pt = ( Pt2 > 0.0 ? std::sqrt( Pt2 ) : 0.0 );
174 G4double phi = G4UniformRand() * twopi;
175 return G4ThreeVector( Pt * std::cos( phi ), Pt * std::sin( phi ), 0.0 );
176 }
177
178
179 //============================================================================
180
181 G4ElasticHNScattering::G4ElasticHNScattering( const G4ElasticHNScattering& ) {
182 throw G4HadronicException( __FILE__, __LINE__,
183 "G4ElasticHNScattering copy constructor not meant to be called" );
184 }
185
186
187 //============================================================================
188
189 G4ElasticHNScattering::~G4ElasticHNScattering() {}
190
191
192 //============================================================================
193
194 const G4ElasticHNScattering & G4ElasticHNScattering::operator=( const G4ElasticHNScattering& ) {
195 throw G4HadronicException( __FILE__, __LINE__,
196 "G4ElasticHNScattering = operator not meant to be called" );
197 }
198
199
200 //============================================================================
201
202 G4bool G4ElasticHNScattering::operator==( const G4ElasticHNScattering& ) const {
203 throw G4HadronicException( __FILE__, __LINE__,
204 "G4ElasticHNScattering == operator not meant to be called" );
205 }
206
207
208 //============================================================================
209
210 G4bool G4ElasticHNScattering::operator!=( const G4ElasticHNScattering& ) const {
211 throw G4HadronicException( __FILE__, __LINE__,
212 "G4ElasticHNScattering != operator not meant to be called" );
213 }
214
215