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68ca986e | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
7 | * Permission to use, copy, modify and distribute this software and its * | |
8 | * documentation strictly for non-commercial purposes is hereby granted * | |
9 | * without fee, provided that the above copyright notice appears in all * | |
10 | * copies and that both the copyright notice and this permission notice * | |
11 | * appear in the supporting documentation. The authors make no claims * | |
12 | * about the suitability of this software for any purpose. It is * | |
13 | * provided "as is" without express or implied warranty. * | |
14 | **************************************************************************/ | |
15 | ||
88cb7938 | 16 | /* $Id$ */ |
116cbefd | 17 | |
94de3818 | 18 | #include <assert.h> |
19 | ||
116cbefd | 20 | #include <TDatabasePDG.h> |
68ca986e | 21 | #include <TLorentzVector.h> |
116cbefd | 22 | #include <TMCProcess.h> |
23 | #include <TPDGCode.h> | |
24 | #include <TRandom.h> | |
68ca986e | 25 | #include <TVector3.h> |
26 | ||
68ca986e | 27 | #include "AliConst.h" |
116cbefd | 28 | #include "AliGenZDC.h" |
68ca986e | 29 | #include "AliRun.h" |
30 | ||
31 | ClassImp(AliGenZDC) | |
32 | ||
33 | //_____________________________________________________________________________ | |
34 | AliGenZDC::AliGenZDC() | |
35 | :AliGenerator() | |
36 | { | |
37 | // | |
38 | // Default constructor | |
39 | // | |
40 | fIpart = 0; | |
41 | } | |
42 | ||
43 | //_____________________________________________________________________________ | |
44 | AliGenZDC::AliGenZDC(Int_t npart) | |
45 | :AliGenerator(npart) | |
46 | { | |
47 | // | |
48 | // Standard constructor | |
49 | // | |
50 | fName = "AliGenZDC"; | |
51 | fTitle = "Generation of Test Particles for ZDCs"; | |
52 | fIpart = kNeutron; | |
53 | fCosx = 0.; | |
54 | fCosy = 0.; | |
55 | fCosz = 1.; | |
56 | fPseudoRapidity = 0.; | |
5a881c97 | 57 | |
68ca986e | 58 | fFermiflag = 1; |
59 | // LHC values for beam divergence and crossing angle | |
60 | fBeamDiv = 0.000032; | |
61 | fBeamCrossAngle = 0.0001; | |
62 | fBeamCrossPlane = 2; | |
5a881c97 | 63 | |
64 | Int_t i, j; | |
65 | for(i=0; i<201; i++){ | |
66 | fProbintp[i] = 0; | |
67 | fProbintn[i] = 0; | |
68 | } | |
69 | for(j=0; j<3; j++){ | |
70 | fPp[i] = 0; | |
71 | } | |
72 | fDebugOpt = 0; | |
68ca986e | 73 | } |
74 | ||
75 | //_____________________________________________________________________________ | |
76 | void AliGenZDC::Init() | |
77 | { | |
5a881c97 | 78 | printf("\n\n AliGenZDC initialized with:\n"); |
866ab5a2 | 79 | printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle " |
68ca986e | 80 | "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle, |
81 | fBeamCrossPlane); | |
5a881c97 | 82 | |
68ca986e | 83 | //Initialize Fermi momentum distributions for Pb-Pb |
84 | FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn); | |
85 | } | |
86 | ||
87 | //_____________________________________________________________________________ | |
88 | void AliGenZDC::Generate() | |
89 | { | |
90 | // | |
91 | // Generate one trigger (n or p) | |
92 | // | |
c0ceba4c | 93 | Int_t i; |
94 | ||
5a881c97 | 95 | Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3]; |
96 | Float_t fPTrack[3], ptot = fPMin; | |
68ca986e | 97 | Int_t nt; |
98 | ||
866ab5a2 | 99 | if(fPseudoRapidity==0.){ |
68ca986e | 100 | pLab[0] = ptot*fCosx; |
101 | pLab[1] = ptot*fCosy; | |
102 | pLab[2] = ptot*fCosz; | |
103 | } | |
104 | else{ | |
105 | Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity))); | |
106 | pLab[0] = -ptot*TMath::Sin(scang); | |
107 | pLab[1] = 0.; | |
108 | pLab[2] = ptot*TMath::Cos(scang); | |
109 | } | |
c0ceba4c | 110 | for(i=0; i<=2; i++){ |
68ca986e | 111 | fP[i] = pLab[i]; |
112 | } | |
113 | ||
5a881c97 | 114 | |
68ca986e | 115 | // Beam divergence and crossing angle |
866ab5a2 | 116 | if(fBeamCrossAngle!=0.) { |
117 | BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab); | |
118 | for(i=0; i<=2; i++){ | |
119 | fP[i] = pLab[i]; | |
120 | } | |
121 | } | |
122 | if(fBeamDiv!=0.) { | |
123 | BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab); | |
124 | for(i=0; i<=2; i++){ | |
125 | fP[i] = pLab[i]; | |
126 | } | |
127 | } | |
128 | ||
68ca986e | 129 | // If required apply the Fermi momentum |
130 | if(fFermiflag==1){ | |
131 | if((fIpart==kProton) || (fIpart==kNeutron)){ | |
132 | ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp); | |
133 | } | |
5a881c97 | 134 | Mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass(); |
135 | fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+Mass*Mass); | |
c0ceba4c | 136 | for(i=0; i<=2; i++){ |
68ca986e | 137 | dddp[i] = ddp[i]; |
138 | } | |
5a881c97 | 139 | dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass); |
68ca986e | 140 | |
866ab5a2 | 141 | TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0); |
68ca986e | 142 | TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0); |
143 | ||
68ca986e | 144 | pFermi.Boost(b); |
c0ceba4c | 145 | for(i=0; i<=2; i++){ |
68ca986e | 146 | fBoostP[i] = pFermi[i]; |
866ab5a2 | 147 | fP[i] = pFermi[i]; |
68ca986e | 148 | } |
149 | ||
150 | } | |
866ab5a2 | 151 | |
152 | for(i=0; i<=2; i++){ | |
153 | fPTrack[i] = fP[i]; | |
154 | } | |
155 | ||
68ca986e | 156 | Float_t polar[3] = {0,0,0}; |
866ab5a2 | 157 | gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0, |
1de555dc | 158 | kPPrimary,nt); |
5a881c97 | 159 | if(fDebugOpt == 1){ |
160 | printf("\n\n Track momentum:\n"); | |
161 | printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]); | |
162 | } | |
68ca986e | 163 | } |
164 | ||
165 | //_____________________________________________________________________________ | |
5a881c97 | 166 | void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp, |
167 | Double_t *fProbintp, Double_t *fProbintn) | |
68ca986e | 168 | { |
169 | // | |
170 | // Momenta distributions according to the "double-gaussian" | |
171 | // distribution (Ilinov) - equal for protons and neutrons | |
172 | // | |
5a881c97 | 173 | |
68ca986e | 174 | fProbintp[0] = 0; |
175 | fProbintn[0] = 0; | |
176 | Double_t sig1 = 0.113; | |
177 | Double_t sig2 = 0.250; | |
178 | Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3)); | |
179 | Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5))); | |
180 | ||
181 | for(Int_t i=1; i<=200; i++){ | |
182 | Double_t p = i*0.005; | |
183 | fPp[i] = p; | |
68ca986e | 184 | Double_t e1 = (p*p)/(2.*sig1*sig1); |
185 | Double_t e2 = (p*p)/(2.*sig2*sig2); | |
186 | Double_t f1 = TMath::Exp(-(e1)); | |
187 | Double_t f2 = TMath::Exp(-(e2)); | |
188 | Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+ | |
189 | alfa*f2/(TMath::Power(sig2,3.)))*0.005; | |
68ca986e | 190 | fProbintp[i] = fProbintp[i-1] + probp; |
191 | fProbintn[i] = fProbintp[i]; | |
5a881c97 | 192 | } |
193 | if(fDebugOpt == 1){ | |
194 | printf("\n\n Initialization of Fermi momenta distribution \n"); | |
195 | for(Int_t i=0; i<=200; i++){ | |
196 | printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]); | |
197 | } | |
68ca986e | 198 | } |
199 | } | |
200 | //_____________________________________________________________________________ | |
5a881c97 | 201 | void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp, |
202 | Double_t *fProbintn, Double_t *ddp) | |
68ca986e | 203 | { |
204 | // | |
205 | // Compute Fermi momentum for spectator nucleons | |
206 | // | |
5a881c97 | 207 | |
68ca986e | 208 | Int_t i; |
209 | Float_t xx = gRandom->Rndm(); | |
699b37ac | 210 | assert ( id==kProton || id==kNeutron ); |
68ca986e | 211 | if(id==kProton){ |
0ff3ad02 | 212 | for(i=1; i<=200; i++){ |
68ca986e | 213 | if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break; |
214 | } | |
215 | } | |
94de3818 | 216 | else { |
68ca986e | 217 | for(i=0; i<=200; i++){ |
218 | if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break; | |
219 | } | |
220 | } | |
221 | Float_t pext = fPp[i]+0.001; | |
222 | Float_t phi = k2PI*(gRandom->Rndm()); | |
223 | Float_t cost = (1.-2.*(gRandom->Rndm())); | |
224 | Float_t tet = TMath::ACos(cost); | |
225 | ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi); | |
226 | ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi); | |
227 | ddp[2] = pext*cost; | |
5a881c97 | 228 | |
229 | if(fDebugOpt == 1){ | |
230 | printf("\n\n Extraction of Fermi momentum\n"); | |
231 | printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]); | |
232 | } | |
68ca986e | 233 | } |
234 | ||
235 | //_____________________________________________________________________________ | |
236 | void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle, | |
5a881c97 | 237 | Int_t fBeamCrossPlane, Double_t *pLab) |
68ca986e | 238 | { |
866ab5a2 | 239 | Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum; |
68ca986e | 240 | Double_t rvec; |
c0ceba4c | 241 | |
242 | Int_t i; | |
68ca986e | 243 | Double_t pmq = 0.; |
c0ceba4c | 244 | for(i=0; i<=2; i++){ |
68ca986e | 245 | pmq = pmq+pLab[i]*pLab[i]; |
246 | } | |
247 | Double_t pmod = TMath::Sqrt(pmq); | |
68ca986e | 248 | |
68ca986e | 249 | if(icross==0){ |
250 | rvec = gRandom->Gaus(0.0,1.0); | |
251 | tetdiv = fBeamDiv * TMath::Abs(rvec); | |
252 | fidiv = (gRandom->Rndm())*k2PI; | |
253 | } | |
254 | else if(icross==1){ | |
255 | if(fBeamCrossPlane==0.){ | |
256 | tetdiv = 0.; | |
257 | fidiv = 0.; | |
258 | } | |
259 | else if(fBeamCrossPlane==1.){ | |
260 | tetdiv = fBeamCrossAngle; | |
261 | fidiv = 0.; | |
262 | } | |
263 | else if(fBeamCrossPlane==2.){ | |
264 | tetdiv = fBeamCrossAngle; | |
736c9b58 | 265 | fidiv = k2PI/4.; |
68ca986e | 266 | } |
267 | } | |
866ab5a2 | 268 | |
269 | tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]); | |
270 | if(pLab[1]!=0. || pLab[0]!=0.){ | |
271 | fipart = TMath::ATan2(pLab[1],pLab[0]); | |
68ca986e | 272 | } |
273 | else{ | |
274 | fipart = 0.; | |
275 | } | |
276 | if(fipart<0.) {fipart = fipart+k2PI;} | |
68ca986e | 277 | tetdiv = tetdiv*kRaddeg; |
278 | fidiv = fidiv*kRaddeg; | |
279 | tetpart = tetpart*kRaddeg; | |
280 | fipart = fipart*kRaddeg; | |
281 | AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum); | |
282 | tetsum = angleSum[0]; | |
283 | fisum = angleSum[1]; | |
68ca986e | 284 | tetsum = tetsum*kDegrad; |
285 | fisum = fisum*kDegrad; | |
286 | pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum); | |
287 | pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum); | |
288 | pLab[2] = pmod*TMath::Cos(tetsum); | |
5a881c97 | 289 | if(fDebugOpt == 1){ |
290 | printf("\n\n Beam divergence and crossing angle\n"); | |
291 | for(i=0; i<=2; i++){ | |
292 | printf(" pLab[%d] = %f\n",i,pLab[i]); | |
293 | } | |
68ca986e | 294 | } |
295 | } | |
296 | ||
297 | //_____________________________________________________________________________ | |
298 | void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2, | |
5a881c97 | 299 | Double_t phi2, Double_t *angleSum) |
68ca986e | 300 | { |
301 | Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2; | |
302 | Double_t rtetsum, tetsum, fisum; | |
303 | ||
304 | temp = -1.; | |
305 | conv = 180./TMath::ACos(temp); | |
306 | ||
307 | ct1 = TMath::Cos(theta1/conv); | |
308 | st1 = TMath::Sin(theta1/conv); | |
309 | cp1 = TMath::Cos(phi1/conv); | |
310 | sp1 = TMath::Sin(phi1/conv); | |
311 | ct2 = TMath::Cos(theta2/conv); | |
312 | st2 = TMath::Sin(theta2/conv); | |
313 | cp2 = TMath::Cos(phi2/conv); | |
314 | sp2 = TMath::Sin(phi2/conv); | |
315 | cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2; | |
316 | cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2; | |
317 | cz = ct1*ct2-st1*st2*cp2; | |
318 | ||
319 | rtetsum = TMath::ACos(cz); | |
320 | tetsum = conv*rtetsum; | |
321 | if(tetsum==0. || tetsum==180.){ | |
322 | fisum = 0.; | |
323 | return; | |
324 | } | |
325 | temp = cx/TMath::Sin(rtetsum); | |
326 | if(temp>1.) temp=1.; | |
327 | if(temp<-1.) temp=-1.; | |
328 | fisum = conv*TMath::ACos(temp); | |
329 | if(cy<0) {fisum = 360.-fisum;} | |
68ca986e | 330 | angleSum[0] = tetsum; |
331 | angleSum[1] = fisum; | |
332 | } | |
333 |