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26 // 26 //
>> 27 // $Id$
27 // ------------------------------------------- 28 // ------------------------------------------------------------
28 // GEANT 4 class implemetation file 29 // GEANT 4 class implemetation file
29 // 30 //
30 // ---------------- G4SingleDiffractiveEx 31 // ---------------- G4SingleDiffractiveExcitation --------------
31 // by Gunter Folger, October 1998. 32 // by Gunter Folger, October 1998.
32 // diffractive Excitation used by strings 33 // diffractive Excitation used by strings models
33 // Take a projectile and a target 34 // Take a projectile and a target
34 // excite the projectile and target 35 // excite the projectile and target
35 // ------------------------------------------- 36 // ------------------------------------------------------------
36 37
37 #include "G4SingleDiffractiveExcitation.hh" 38 #include "G4SingleDiffractiveExcitation.hh"
38 #include "globals.hh" 39 #include "globals.hh"
39 #include "G4PhysicalConstants.hh" 40 #include "G4PhysicalConstants.hh"
40 #include "G4SystemOfUnits.hh" 41 #include "G4SystemOfUnits.hh"
41 #include "Randomize.hh" 42 #include "Randomize.hh"
42 #include "G4LorentzRotation.hh" 43 #include "G4LorentzRotation.hh"
43 #include "G4ThreeVector.hh" 44 #include "G4ThreeVector.hh"
44 #include "G4ParticleDefinition.hh" 45 #include "G4ParticleDefinition.hh"
45 #include "G4VSplitableHadron.hh" 46 #include "G4VSplitableHadron.hh"
46 #include "G4ExcitedString.hh" 47 #include "G4ExcitedString.hh"
47 48
48 #include "G4Log.hh" << 49 G4SingleDiffractiveExcitation::G4SingleDiffractiveExcitation(G4double sigmaPt, G4double minextraMass,G4double x0mass)
49 #include "G4Pow.hh" << 50 :
>> 51 widthOfPtSquare(-2*sqr(sigmaPt)) , minExtraMass(minextraMass),
>> 52 minmass(x0mass)
>> 53 {}
50 54
51 //#define debugSingleDiffraction << 55 G4SingleDiffractiveExcitation::~G4SingleDiffractiveExcitation()
52 << 56 {}
53 G4SingleDiffractiveExcitation::G4SingleDiffrac <<
54 <<
55 G4SingleDiffractiveExcitation::~G4SingleDiffra <<
56 57
57 G4bool G4SingleDiffractiveExcitation:: 58 G4bool G4SingleDiffractiveExcitation::
58 ExciteParticipants( G4VSplitableHadron *projec << 59 ExciteParticipants(G4VSplitableHadron *projectile, G4VSplitableHadron *target) const
59 G4bool ProjectileDiffracti <<
60 { 60 {
61 #ifdef debugSingleDiffraction <<
62 G4cout<<G4endl<<"G4SingleDiffractiveExcita <<
63 #endif <<
64 <<
65 G4LorentzVector Pprojectile=projectile->Get4 <<
66 G4double Mprojectile = projectile->GetDef <<
67 G4double Mprojectile2=sqr(projectile->GetDef <<
68 <<
69 G4LorentzVector Ptarget=target->Get4Momentum <<
70 G4double Mtarget = target->GetDefinition( <<
71 G4double Mtarget2=sqr(target->GetDefinition( <<
72 <<
73 #ifdef debugSingleDiffraction <<
74 G4cout<<"Proj Targ "<<projectile->GetDefin <<
75 G4cout<<"Pr Tr 4-Mom "<<Pprojectile<<" "<< <<
76 <<" "<<Ptarget <<" "<< <<
77 #endif <<
78 <<
79 G4LorentzVector Psum=Pprojectile+Ptarget; <<
80 G4double SqrtS=Psum.mag(); <<
81 G4double S =Psum.mag2(); <<
82 <<
83 #ifdef debugSingleDiffraction <<
84 G4cout<<"SqrtS-Mprojectile-Mtarget "<<Sqrt <<
85 <<" "<<SqrtS-Mprojectile-Mtarget<<G4 <<
86 #endif <<
87 if (SqrtS-Mprojectile-Mtarget <= 250.0*MeV) <<
88 #ifdef debugSingleDiffraction <<
89 G4cerr<<"Projectile: "<<projectile->GetDef <<
90 <<Pprojectile<<" "<<Pprojectile.mag( <<
91 G4cerr<<"Target: "<<target->GetDefinit <<
92 <<Ptarget<<" "<<Ptarget.mag()<<G4end <<
93 G4cerr<<"sqrt(S) = "<<SqrtS<<" Mp + Mt = " <<
94 #endif <<
95 return true; <<
96 } <<
97 <<
98 G4LorentzRotation toCms(-1*Psum.boostVector( <<
99 <<
100 G4LorentzVector Ptmp=toCms*Pprojectile; <<
101 <<
102 if ( Ptmp.pz() <= 0. ) <<
103 { <<
104 // "String" moving backwards in CMS, abor <<
105 // G4cout << " abort Collision!! " <<
106 return false; <<
107 } <<
108 <<
109 toCms.rotateZ(-1*Ptmp.phi()); <<
110 toCms.rotateY(-1*Ptmp.theta()); <<
111 <<
112 G4LorentzRotation toLab(toCms.inverse()); <<
113 <<
114 Pprojectile.transform(toCms); <<
115 Ptarget.transform(toCms); <<
116 #ifdef debugSingleDiffraction <<
117 G4cout << "Pprojectile in CMS " << Pproje <<
118 G4cout << "Ptarget in CMS " << Ptarge <<
119 #endif <<
120 G4double maxPtSquare=sqr(Ptarget.pz()); <<
121 <<
122 G4double ProjectileMinDiffrMass(0.), TargetM <<
123 G4double AveragePt2(0.); <<
124 G4int absPDGcode=std::abs(projectile->GetDef <<
125 <<
126 if ( ProjectileDiffraction ) { <<
127 if ( absPDGcode > 1000 ) <<
128 { <<
129 if ( absPDGcode > 4000 && absPDGcode < 6 <<
130 { <<
131 ProjectileMinDiffrMass = projectile->G <<
132 AveragePt2 = 0.3; <<
133 } <<
134 else <<
135 { <<
136 ProjectileMinDiffrMass = 1.16; <<
137 AveragePt2 = 0.3; <<
138 } <<
139 } <<
140 else if( absPDGcode == 211 || absPDGcode = <<
141 { <<
142 ProjectileMinDiffrMass = 1.0; <<
143 AveragePt2 = 0.3; <<
144 } <<
145 else if( absPDGcode == 321 || absPDGcode = <<
146 { <<
147 ProjectileMinDiffrMass = 1.1; <<
148 AveragePt2 = 0.3; <<
149 } <<
150 else if( absPDGcode == 22) <<
151 { <<
152 ProjectileMinDiffrMass = 0.25; <<
153 AveragePt2 = 0.36; <<
154 } <<
155 else if( absPDGcode > 400 && absPDGcode < <<
156 { <<
157 ProjectileMinDiffrMass = projectile->Get <<
158 AveragePt2 = 0.3; <<
159 } <<
160 else <<
161 { <<
162 ProjectileMinDiffrMass = 1.1; <<
163 AveragePt2 = 0.3; <<
164 }; <<
165 <<
166 ProjectileMinDiffrMass = ProjectileMinDiff <<
167 Mprojectile2=sqr(ProjectileMinDiffrMass); <<
168 } <<
169 else <<
170 { <<
171 TargetMinDiffrMass = 1.16*GeV; <<
172 Mtarget2 = sqr( TargetMinDiffrMass) ; <<
173 AveragePt2 = 0.3; <<
174 } // end of if ( ProjectileDiffraction ) <<
175 <<
176 AveragePt2 = AveragePt2 * GeV*GeV; <<
177 <<
178 G4double Pt2, PZcms, PZcms2; <<
179 G4double ProjMassT2, ProjMassT; <<
180 G4double TargMassT2, TargMassT; <<
181 G4double PMinusMin, PMinusMax; <<
182 G4double TPlusMin, TPlusMax; <<
183 G4double PMinusNew, PPlusNew, TPlusNew, TMin <<
184 <<
185 G4LorentzVector Qmomentum; <<
186 G4double Qminus, Qplus; <<
187 <<
188 G4int whilecount=0; <<
189 do { <<
190 whilecount++; <<
191 <<
192 if (whilecount > 1000 ) <<
193 { <<
194 Qmomentum=G4LorentzVector(0.,0.,0.,0.); <<
195 return false; // Ignore this intera <<
196 } <<
197 <<
198 // Generate pt <<
199 Qmomentum=G4LorentzVector(GaussianPt(Avera <<
200 <<
201 Pt2 = G4ThreeVector( Qmomentum.vect() ).ma <<
202 <<
203 ProjMassT2 = Mprojectile2 + Pt2; <<
204 ProjMassT = std::sqrt( ProjMassT2 ); <<
205 TargMassT2 = Mtarget2 + Pt2; <<
206 TargMassT = std::sqrt( TargMassT2 ); <<
207 <<
208 #ifdef debugSingleDiffraction <<
209 G4cout<<whilecount<<" "<<Pt2<<" "<<ProjM <<
210 #endif <<
211 if ( SqrtS < ProjMassT + TargMassT ) conti <<
212 <<
213 PZcms2 = ( S*S + ProjMassT2*ProjMassT2 + T <<
214 - 2.0*S*ProjMassT2 - 2.0*S*TargM <<
215 <<
216 if ( PZcms2 < 0 ) continue; <<
217 <<
218 PZcms = std::sqrt( PZcms2 ); <<
219 <<
220 if ( ProjectileDiffraction ) <<
221 { // The projectile will fragment, t <<
222 PMinusMin = std::sqrt( ProjMassT2 + PZcm <<
223 PMinusMax = SqrtS - TargMassT; <<
224 <<
225 PMinusNew = ChooseX( PMinusMin, PMinusMa <<
226 TMinusNew = SqrtS - PMinusNew; <<
227 <<
228 Qminus = Ptarget.minus() - TMinusNew; <<
229 TPlusNew = TargMassT2 / TMinusNew; <<
230 Qplus = Ptarget.plus() - TPlusNew; <<
231 <<
232 } else { // The target will fragment, the <<
233 TPlusMin = std::sqrt( TargMassT2 + PZcms <<
234 TPlusMax = SqrtS - ProjMassT; <<
235 <<
236 TPlusNew = ChooseX( TPlusMin, TPlusMax ) <<
237 PPlusNew = SqrtS - TPlusNew; <<
238 <<
239 Qplus = PPlusNew - Pprojectile.plus(); <<
240 PMinusNew = ProjMassT2 / PPlusNew; <<
241 Qminus = PMinusNew - Pprojectile.minus() <<
242 } <<
243 <<
244 Qmomentum.setPz( (Qplus - Qminus)/2 ); <<
245 Qmomentum.setE( (Qplus + Qminus)/2 ); <<
246 <<
247 #ifdef debugSingleDiffraction <<
248 G4cout<<ProjectileDiffraction<<" "<<( Pp <<
249 G4cout<<!ProjectileDiffraction<<" "<<( P <<
250 #endif <<
251 <<
252 } while ( ( ProjectileDiffraction&&( Pprojec <<
253 (!ProjectileDiffraction&&( Ptarget <<
254 // Repeat the sampling because there was n <<
255 <<
256 Pprojectile += Qmomentum; <<
257 <<
258 Ptarget -= Qmomentum; <<
259 <<
260 // Transform back and update SplitableHadron <<
261 Pprojectile.transform(toLab); <<
262 Ptarget.transform(toLab); <<
263 <<
264 #ifdef debugSingleDiffraction <<
265 G4cout << "Pprojectile in Lab. " << Pproj <<
266 G4cout << "Ptarget in Lab. " << Ptarg <<
267 G4cout << "G4SingleDiffractiveExcitation- <<
268 G4cout << "G4SingleDiffractiveExcitation- <<
269 #endif <<
270 61
271 target->Set4Momentum(Ptarget); << 62 G4LorentzVector Pprojectile=projectile->Get4Momentum();
272 projectile->Set4Momentum(Pprojectile); << 63 G4double Mprojectile2=sqr(projectile->GetDefinition()->GetPDGMass() + minExtraMass);
>> 64
>> 65 G4LorentzVector Ptarget=target->Get4Momentum();
>> 66 G4double Mtarget2=sqr(target->GetDefinition()->GetPDGMass() + minExtraMass);
>> 67 // G4cout << "E proj, target :" << Pprojectile.e() << ", " <<
>> 68 // Ptarget.e() << G4endl;
>> 69
>> 70 G4bool KeepProjectile= G4UniformRand() > 0.5;
>> 71
>> 72 // reset the min.mass of the non diffractive particle to its value, ( minus a bit for rounding...)
>> 73 if ( KeepProjectile )
>> 74 {
>> 75 // cout << " Projectile fix" << G4endl;
>> 76 Mprojectile2 = sqr(projectile->GetDefinition()->GetPDGMass() * (1-perCent) );
>> 77 } else {
>> 78 // cout << " Target fix" << G4endl;
>> 79 Mtarget2=sqr(target->GetDefinition()->GetPDGMass() * (1-perCent) );
>> 80 }
>> 81
>> 82 // Transform momenta to cms and then rotate parallel to z axis;
>> 83
>> 84 G4LorentzVector Psum;
>> 85 Psum=Pprojectile+Ptarget;
>> 86
>> 87 G4LorentzRotation toCms(-1*Psum.boostVector());
>> 88
>> 89 G4LorentzVector Ptmp=toCms*Pprojectile;
>> 90
>> 91 if ( Ptmp.pz() <= 0. )
>> 92 {
>> 93 // "String" moving backwards in CMS, abort collision !!
>> 94 // G4cout << " abort Collision!! " << G4endl;
>> 95 return false;
>> 96 }
>> 97
>> 98 toCms.rotateZ(-1*Ptmp.phi());
>> 99 toCms.rotateY(-1*Ptmp.theta());
>> 100
>> 101 // G4cout << "Pprojectile be4 boost " << Pprojectile << G4endl;
>> 102 // G4cout << "Ptarget be4 boost : " << Ptarget << G4endl;
>> 103
>> 104
>> 105
>> 106 G4LorentzRotation toLab(toCms.inverse());
>> 107
>> 108 Pprojectile.transform(toCms);
>> 109 Ptarget.transform(toCms);
>> 110
>> 111 G4LorentzVector Qmomentum;
>> 112 G4int whilecount=0;
>> 113 do {
>> 114 // Generate pt
>> 115
>> 116 G4double maxPtSquare=sqr(Ptarget.pz());
>> 117 if (whilecount++ >= 500 && (whilecount%100)==0)
>> 118 // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants possibly looping"
>> 119 // << ", loop count/ maxPtSquare : "
>> 120 // << whilecount << " / " << maxPtSquare << G4endl;
>> 121 if (whilecount > 1000 )
>> 122 {
>> 123 Qmomentum=G4LorentzVector(0.,0.,0.,0.);
>> 124 // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants: Aborting loop!" << G4endl;
>> 125 return false; // Ignore this interaction
>> 126 }
>> 127 Qmomentum=G4LorentzVector(GaussianPt(widthOfPtSquare,maxPtSquare),0);
>> 128
>> 129
>> 130 // Momentum transfer
>> 131 G4double Xmin = minmass / ( Pprojectile.e() + Ptarget.e() );
>> 132 G4double Xmax=1.;
>> 133 G4double Xplus =ChooseX(Xmin,Xmax);
>> 134 G4double Xminus=ChooseX(Xmin,Xmax);
>> 135
>> 136 G4double pt2=G4ThreeVector(Qmomentum.vect()).mag2();
>> 137 G4double Qplus =-1 * pt2 / Xminus/Ptarget.minus();
>> 138 G4double Qminus= pt2 / Xplus /Pprojectile.plus();
>> 139
>> 140 if ( KeepProjectile )
>> 141 {
>> 142 Qminus = (sqr(projectile->GetDefinition()->GetPDGMass()) + pt2 )
>> 143 / (Pprojectile.plus() + Qplus )
>> 144 - Pprojectile.minus();
>> 145 } else
>> 146 {
>> 147 Qplus = Ptarget.plus()
>> 148 - (sqr(target->GetDefinition()->GetPDGMass()) + pt2 )
>> 149 / (Ptarget.minus() - Qminus );
>> 150 }
>> 151
>> 152 Qmomentum.setPz( (Qplus-Qminus)/2 );
>> 153 Qmomentum.setE( (Qplus+Qminus)/2 );
>> 154
>> 155 // G4cout << "Qplus / Qminus " << Qplus << " / " << Qminus<<G4endl;
>> 156 // G4cout << "pt2 " << pt2 << G4endl;
>> 157 // G4cout << "Qmomentum " << Qmomentum << G4endl;
>> 158 // G4cout << " Masses (P/T) : " << (Pprojectile+Qmomentum).mag() <<
>> 159 // " / " << (Ptarget-Qmomentum).mag() << G4endl;
>> 160
>> 161 } while ( (Ptarget-Qmomentum).mag2() <= Mtarget2
>> 162 || (Pprojectile+Qmomentum).mag2() <= Mprojectile2
>> 163 || (Ptarget-Qmomentum).e() < 0.
>> 164 || (Pprojectile+Qmomentum).e() < 0. );
273 165
274 return true; << 166
>> 167 // G4double Ecms=Pprojectile.e() + Ptarget.e();
>> 168
>> 169 Pprojectile += Qmomentum;
>> 170
>> 171 Ptarget -= Qmomentum;
>> 172
>> 173 // G4cout << "Pprojectile.e() : " << Pprojectile.e() << G4endl;
>> 174 // G4cout << "Ptarget.e() : " << Ptarget.e() << G4endl;
>> 175
>> 176 // G4cout << "end event_______________________________________________"<<G4endl;
>> 177 //
>> 178
>> 179
>> 180 // G4cout << "Pprojectile with Q : " << Pprojectile << G4endl;
>> 181 // G4cout << "Ptarget with Q : " << Ptarget << G4endl;
>> 182 // G4cout << "Projectile back: " << toLab * Pprojectile << G4endl;
>> 183 // G4cout << "Target back: " << toLab * Ptarget << G4endl;
>> 184
>> 185 // Transform back and update SplitableHadron Participant.
>> 186 Pprojectile.transform(toLab);
>> 187 Ptarget.transform(toLab);
>> 188
>> 189 // G4cout << "G4SingleDiffractiveExcitation- Target mass " << Ptarget.mag() << G4endl;
>> 190 // G4cout << "G4SingleDiffractiveExcitation- Projectile mass " << Pprojectile.mag() << G4endl;
>> 191
>> 192 target->Set4Momentum(Ptarget);
>> 193 projectile->Set4Momentum(Pprojectile);
>> 194
>> 195
>> 196 return true;
275 } 197 }
276 198
>> 199
>> 200
>> 201
277 // --------- private methods ----------------- 202 // --------- private methods ----------------------
278 203
279 G4double G4SingleDiffractiveExcitation::Choose 204 G4double G4SingleDiffractiveExcitation::ChooseX(G4double Xmin, G4double Xmax) const
280 { 205 {
281 // choose an x between Xmin and Xmax with P( << 206 // choose an x between Xmin and Xmax with P(x) ~ 1/x
282 G4double range=Xmax-Xmin; <<
283 207
284 if ( Xmin <= 0. || range <=0. ) << 208 // to be improved...
285 { << 209
286 G4cout << " Xmin, range : " << Xmin << " , << 210 G4double range=Xmax-Xmin;
287 throw G4HadronicException(__FILE__, __LINE << 211
288 } << 212 if ( Xmin <= 0. || range <=0. )
289 << 213 {
290 G4double x = Xmin*G4Pow::GetInstance()->powA << 214 G4cout << " Xmin, range : " << Xmin << " , " << range << G4endl;
291 // G4double x = 1.0/sqr(1.0/std::sqrt(Xmin) << 215 throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation::ChooseX : Invalid arguments ");
292 return x; << 216 }
293 } <<
294 217
>> 218 G4double x;
>> 219 do {
>> 220 x=Xmin + G4UniformRand() * range;
>> 221 } while ( Xmin/x < G4UniformRand() );
>> 222
>> 223 // cout << "DiffractiveX "<<x<<G4endl;
>> 224 return x;
>> 225 }
295 226
296 G4ThreeVector G4SingleDiffractiveExcitation::G 227 G4ThreeVector G4SingleDiffractiveExcitation::GaussianPt(G4double widthSquare, G4double maxPtSquare) const
297 { // @@ this method is used in FTF 228 { // @@ this method is used in FTFModel as well. Should go somewhere common!
298 229
299 G4double pt2; << 230 G4double pt2;
300 231
301 const G4int maxNumberOfLoops = 1000; << 232 do {
302 G4int loopCounter = 0; << 233 pt2=widthSquare * std::log( G4UniformRand() );
303 do { << 234 } while ( pt2 > maxPtSquare);
304 pt2=-widthSquare * G4Log( G4UniformRand() <<
305 } while ( ( pt2 > maxPtSquare) && ++loopCoun <<
306 if ( loopCounter >= maxNumberOfLoops ) { <<
307 pt2 = 0.99*maxPtSquare; // Just an accept <<
308 } <<
309 235
310 pt2=std::sqrt(pt2); << 236 pt2=std::sqrt(pt2);
311 237
312 G4double phi=G4UniformRand() * twopi; << 238 G4double phi=G4UniformRand() * twopi;
313 239
314 return G4ThreeVector (pt2*std::cos(phi), pt2 << 240 return G4ThreeVector (pt2*std::cos(phi), pt2*std::sin(phi), 0.);
315 } 241 }
>> 242
>> 243
>> 244
>> 245
316 246
317 247