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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 | ||
16 | /* $Id$ */ | |
17 | ||
18 | ////////////////////////////////////////////////////////////////////// | |
19 | // // // | |
20 | // Generator of spectator nucleons (either protons or neutrons)// | |
21 | // computes beam crossing and divergence and Fermi momentum // | |
22 | // // | |
23 | ///////////////////////////////////////////////////////////////////// | |
24 | ||
25 | #include <assert.h> | |
26 | ||
27 | #include <TDatabasePDG.h> | |
28 | #include <TLorentzVector.h> | |
29 | #include <TMCProcess.h> | |
30 | #include <TPDGCode.h> | |
31 | #include <TRandom.h> | |
32 | #include <TVector3.h> | |
33 | ||
34 | #include "AliConst.h" | |
35 | #include "AliGenZDC.h" | |
36 | #include "AliRun.h" | |
37 | #include "AliMC.h" | |
38 | ||
39 | ClassImp(AliGenZDC) | |
40 | ||
41 | //_____________________________________________________________________________ | |
42 | AliGenZDC::AliGenZDC() | |
43 | :AliGenerator(), | |
44 | fIpart(0), | |
45 | fCosx(0), | |
46 | fCosy(0), | |
47 | fCosz(0), | |
48 | fPseudoRapidity(0), | |
49 | fFermiflag(0), | |
50 | fBeamDiv(0), | |
51 | fBeamCrossAngle(0), | |
52 | fBeamCrossPlane(0), | |
53 | fDebugOpt(0) | |
54 | { | |
55 | // | |
56 | // Default constructor | |
57 | // | |
58 | for(Int_t i=0; i<201; i++){ | |
59 | fProbintp[i]=0.; | |
60 | fProbintn[i]=0.; | |
61 | fPp[i]=0.; | |
62 | } | |
63 | } | |
64 | ||
65 | //_____________________________________________________________________________ | |
66 | AliGenZDC::AliGenZDC(Int_t npart) | |
67 | :AliGenerator(npart), | |
68 | fIpart(kNeutron), | |
69 | fCosx(0.), | |
70 | fCosy(0.), | |
71 | fCosz(1.), | |
72 | fPseudoRapidity(0.), | |
73 | fFermiflag(1), | |
74 | fBeamDiv(0.000032), | |
75 | fBeamCrossAngle(0.0001), | |
76 | fBeamCrossPlane(2), | |
77 | fDebugOpt(0) | |
78 | { | |
79 | // | |
80 | // Standard constructor | |
81 | // | |
82 | fName = "AliGenZDC"; | |
83 | fTitle = "Generation of Test Particles for ZDCs"; | |
84 | ||
85 | for(Int_t i=0; i<201; i++){ | |
86 | fProbintp[i] = 0; | |
87 | fProbintn[i] = 0; | |
88 | fPp[i] = 0; | |
89 | } | |
90 | } | |
91 | ||
92 | //_____________________________________________________________________________ | |
93 | void AliGenZDC::Init() | |
94 | { | |
95 | //Initialize Fermi momentum distributions for Pb-Pb | |
96 | // | |
97 | printf("\n\n AliGenZDC initialization:\n"); | |
98 | printf(" Particle: %d, Track cosines: x = %f, y = %f, z = %f \n", | |
99 | fIpart,fCosx,fCosy,fCosz); | |
100 | printf(" Fermi flag = %d, Beam divergence = %f, Crossing angle " | |
101 | "= %f, Crossing plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle, | |
102 | fBeamCrossPlane); | |
103 | ||
104 | FermiTwoGaussian(208.); | |
105 | } | |
106 | ||
107 | //_____________________________________________________________________________ | |
108 | void AliGenZDC::Generate() | |
109 | { | |
110 | // | |
111 | // Generate one trigger (n or p) | |
112 | // | |
113 | Int_t i; | |
114 | ||
115 | Double_t mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3]={0.,0.,0.}, dddp0, dddp[3]; | |
116 | Float_t fPTrack[3], ptot = fPMin; | |
117 | Int_t nt; | |
118 | ||
119 | if(fPseudoRapidity==0.){ | |
120 | pLab[0] = ptot*fCosx; | |
121 | pLab[1] = ptot*fCosy; | |
122 | pLab[2] = ptot*fCosz; | |
123 | } | |
124 | else{ | |
125 | Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity))); | |
126 | pLab[0] = -ptot*TMath::Sin(scang); | |
127 | pLab[1] = 0.; | |
128 | pLab[2] = ptot*TMath::Cos(scang); | |
129 | } | |
130 | for(i=0; i<=2; i++) fP[i] = pLab[i]; | |
131 | if(fDebugOpt == 1){ | |
132 | printf("\n\n Particle momentum before divergence and crossing\n"); | |
133 | for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]); | |
134 | } | |
135 | ||
136 | // Beam divergence and crossing angle | |
137 | if(fBeamCrossAngle!=0.) { | |
138 | BeamDivCross(1, pLab); | |
139 | for(i=0; i<=2; i++) fP[i] = pLab[i]; | |
140 | } | |
141 | if(fBeamDiv!=0.) { | |
142 | BeamDivCross(0, pLab); | |
143 | for(i=0; i<=2; i++) fP[i] = pLab[i]; | |
144 | } | |
145 | ||
146 | // If required apply the Fermi momentum | |
147 | if(fFermiflag==1){ | |
148 | if((fIpart==kProton) || (fIpart==kNeutron)) | |
149 | ExtractFermi(fIpart, ddp); | |
150 | mass=TDatabasePDG::Instance()->GetParticle(fIpart)->Mass(); | |
151 | fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+mass*mass); | |
152 | for(i=0; i<=2; i++) dddp[i] = ddp[i]; | |
153 | dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass); | |
154 | ||
155 | TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0); | |
156 | TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0); | |
157 | ||
158 | pFermi.Boost(b); | |
159 | for(i=0; i<=2; i++){ | |
160 | fBoostP[i] = pFermi[i]; | |
161 | fP[i] = pFermi[i]; | |
162 | } | |
163 | ||
164 | } | |
165 | ||
166 | for(i=0; i<=2; i++) fPTrack[i] = fP[i]; | |
167 | ||
168 | Float_t polar[3] = {0,0,0}; | |
169 | gAlice->GetMCApp()->PushTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0, | |
170 | kPPrimary,nt); | |
171 | // ----------------------------------------------------------------------- | |
172 | if(fDebugOpt == 1){ | |
173 | printf("\n\n Track momentum:\n"); | |
174 | printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]); | |
175 | } | |
176 | else if(fDebugOpt == 2){ | |
177 | FILE *file; | |
178 | if((file = fopen("SpectMomentum.dat","a")) == NULL){ | |
179 | printf("Cannot open file SpectMomentum.dat\n"); | |
180 | return; | |
181 | } | |
182 | fprintf(file," %f \t %f \t %f \n",fPTrack[0],fPTrack[1],fPTrack[2]); | |
183 | fclose(file); | |
184 | } | |
185 | ||
186 | } | |
187 | ||
188 | //_____________________________________________________________________________ | |
189 | void AliGenZDC::FermiTwoGaussian(Float_t A) | |
190 | { | |
191 | // | |
192 | // Momenta distributions according to the "double-gaussian" | |
193 | // distribution (Ilinov) - equal for protons and neutrons | |
194 | // | |
195 | ||
196 | Double_t sig1 = 0.113; | |
197 | Double_t sig2 = 0.250; | |
198 | Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3)); | |
199 | Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5))); | |
200 | ||
201 | for(Int_t i=1; i<=200; i++){ | |
202 | Double_t p = i*0.005; | |
203 | fPp[i] = p; | |
204 | Double_t e1 = (p*p)/(2.*sig1*sig1); | |
205 | Double_t e2 = (p*p)/(2.*sig2*sig2); | |
206 | Double_t f1 = TMath::Exp(-(e1)); | |
207 | Double_t f2 = TMath::Exp(-(e2)); | |
208 | Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+ | |
209 | alfa*f2/(TMath::Power(sig2,3.)))*0.005; | |
210 | fProbintp[i] = fProbintp[i-1] + probp; | |
211 | fProbintn[i] = fProbintp[i]; | |
212 | } | |
213 | if(fDebugOpt == 1){ | |
214 | printf("\n\n Initialization of Fermi momenta distribution \n"); | |
215 | //for(Int_t i=0; i<=200; i++) | |
216 | // printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]); | |
217 | } | |
218 | } | |
219 | //_____________________________________________________________________________ | |
220 | void AliGenZDC::ExtractFermi(Int_t id, Double_t *ddp) | |
221 | { | |
222 | // | |
223 | // Compute Fermi momentum for spectator nucleons | |
224 | // | |
225 | ||
226 | Int_t index=0; | |
227 | Float_t xx = gRandom->Rndm(); | |
228 | assert ( id==kProton || id==kNeutron ); | |
229 | if(id==kProton){ | |
230 | for(Int_t i=1; i<=200; i++){ | |
231 | if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break; | |
232 | index = i; | |
233 | } | |
234 | } | |
235 | else { | |
236 | for(Int_t i=1; i<=200; i++){ | |
237 | if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break; | |
238 | index = i; | |
239 | } | |
240 | } | |
241 | Float_t pext = fPp[index]+0.001; | |
242 | Float_t phi = k2PI*(gRandom->Rndm()); | |
243 | Float_t cost = (1.-2.*(gRandom->Rndm())); | |
244 | Float_t tet = TMath::ACos(cost); | |
245 | ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi); | |
246 | ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi); | |
247 | ddp[2] = pext*cost; | |
248 | ||
249 | if(fDebugOpt == 1){ | |
250 | printf("\n\n Extraction of Fermi momentum\n"); | |
251 | printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]); | |
252 | } | |
253 | } | |
254 | ||
255 | //_____________________________________________________________________________ | |
256 | void AliGenZDC::BeamDivCross(Int_t icross, Double_t *pLab) | |
257 | { | |
258 | // Applying beam divergence and crossing angle | |
259 | // | |
260 | Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum; | |
261 | Double_t rvec; | |
262 | ||
263 | Double_t pmq = 0.; | |
264 | Int_t i; | |
265 | for(i=0; i<=2; i++) pmq = pmq+pLab[i]*pLab[i]; | |
266 | Double_t pmod = TMath::Sqrt(pmq); | |
267 | ||
268 | if(icross==0){ // ##### Beam divergence | |
269 | rvec = gRandom->Gaus(0.0,1.0); | |
270 | tetdiv = fBeamDiv * TMath::Abs(rvec); | |
271 | fidiv = (gRandom->Rndm())*k2PI; | |
272 | } | |
273 | else if(icross==1){ // ##### Crossing angle | |
274 | if(fBeamCrossPlane==0){ | |
275 | tetdiv = 0.; | |
276 | fidiv = 0.; | |
277 | } | |
278 | else if(fBeamCrossPlane==1){ // Horizontal crossing plane | |
279 | tetdiv = fBeamCrossAngle; | |
280 | fidiv = 0.; | |
281 | } | |
282 | else if(fBeamCrossPlane==2){ // Vertical crossing plane | |
283 | tetdiv = fBeamCrossAngle; | |
284 | fidiv = k2PI/4.; | |
285 | } | |
286 | } | |
287 | ||
288 | tetpart = TMath::ATan2(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]),pLab[2]); | |
289 | if(pLab[1]!=0. || pLab[0]!=0.) fipart = TMath::ATan2(pLab[1],pLab[0]); | |
290 | else fipart = 0.; | |
291 | if(fipart<0.) {fipart = fipart+k2PI;} | |
292 | tetdiv = tetdiv*kRaddeg; | |
293 | fidiv = fidiv*kRaddeg; | |
294 | tetpart = tetpart*kRaddeg; | |
295 | fipart = fipart*kRaddeg; | |
296 | AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum); | |
297 | tetsum = angleSum[0]; | |
298 | fisum = angleSum[1]; | |
299 | tetsum = tetsum*kDegrad; | |
300 | fisum = fisum*kDegrad; | |
301 | pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum); | |
302 | pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum); | |
303 | pLab[2] = pmod*TMath::Cos(tetsum); | |
304 | if(fDebugOpt == 1){ | |
305 | if(icross==0) printf("\n\n Beam divergence \n"); | |
306 | else printf("\n\n Beam crossing \n"); | |
307 | for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]); | |
308 | } | |
309 | } | |
310 | ||
311 | //_____________________________________________________________________________ | |
312 | void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2, | |
313 | Double_t phi2, Double_t *angleSum) | |
314 | { | |
315 | // Calculating the sum of 2 angles | |
316 | Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2; | |
317 | Double_t rtetsum, tetsum, fisum; | |
318 | ||
319 | temp = -1.; | |
320 | conv = 180./TMath::ACos(temp); | |
321 | ||
322 | ct1 = TMath::Cos(theta1/conv); | |
323 | st1 = TMath::Sin(theta1/conv); | |
324 | cp1 = TMath::Cos(phi1/conv); | |
325 | sp1 = TMath::Sin(phi1/conv); | |
326 | ct2 = TMath::Cos(theta2/conv); | |
327 | st2 = TMath::Sin(theta2/conv); | |
328 | cp2 = TMath::Cos(phi2/conv); | |
329 | sp2 = TMath::Sin(phi2/conv); | |
330 | cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2; | |
331 | cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2; | |
332 | cz = ct1*ct2-st1*st2*cp2; | |
333 | ||
334 | rtetsum = TMath::ACos(cz); | |
335 | tetsum = conv*rtetsum; | |
336 | if(tetsum==0. || tetsum==180.){ | |
337 | fisum = 0.; | |
338 | return; | |
339 | } | |
340 | temp = cx/TMath::Sin(rtetsum); | |
341 | if(temp>1.) temp=1.; | |
342 | if(temp<-1.) temp=-1.; | |
343 | fisum = conv*TMath::ACos(temp); | |
344 | if(cy<0) {fisum = 360.-fisum;} | |
345 | angleSum[0] = tetsum; | |
346 | angleSum[1] = fisum; | |
347 | } | |
348 |