Minor corrections
[u/mrichter/AliRoot.git] / ZDC / AliGenZDC.cxx
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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
16/*
17$Log$
0ff3ad02 18Revision 1.10 2001/09/26 16:00:47 coppedis
19Minor change
20
f3f777b8 21Revision 1.8 2001/04/20 10:10:25 coppedis
22Minor changes
23
c4c7fa06 24Revision 1.7 2001/03/15 16:13:28 coppedis
25Code review
26
5a881c97 27Revision 1.6 2000/11/30 17:16:14 coppedis
28Changes suggested by fca
29
1de555dc 30Revision 1.5 2000/11/22 11:30:12 coppedis
31Major code revision
32
866ab5a2 33Revision 1.4 2000/10/05 08:02:47 fca
34Correction of the generator direction
35
699b37ac 36Revision 1.3 2000/10/02 21:28:20 fca
37Removal of useless dependecies via forward declarations
38
94de3818 39Revision 1.2 2000/07/11 11:12:34 fca
40Some syntax corrections for non standard HP aCC
41
c0ceba4c 42Revision 1.1 2000/07/10 13:58:01 fca
43New version of ZDC from E.Scomparin & C.Oppedisano
44
68ca986e 45Revision 1.7 2000/01/19 17:17:40 fca
46
47Revision 1.6 1999/09/29 09:24:35 fca
48Introduction of the Copyright and cvs Log
49
50*/
94de3818 51#include <assert.h>
52
68ca986e 53#include <TRandom.h>
54#include <TLorentzVector.h>
55#include <TVector3.h>
94de3818 56#include "TDatabasePDG.h"
68ca986e 57
58#include "AliGenZDC.h"
59#include "AliConst.h"
60#include "AliPDG.h"
61#include "AliRun.h"
1de555dc 62#include "AliMCProcess.h"
68ca986e 63
64ClassImp(AliGenZDC)
65
66//_____________________________________________________________________________
67AliGenZDC::AliGenZDC()
68 :AliGenerator()
69{
70 //
71 // Default constructor
72 //
73 fIpart = 0;
74}
75
76//_____________________________________________________________________________
77AliGenZDC::AliGenZDC(Int_t npart)
78 :AliGenerator(npart)
79{
80 //
81 // Standard constructor
82 //
83 fName = "AliGenZDC";
84 fTitle = "Generation of Test Particles for ZDCs";
85 fIpart = kNeutron;
86 fCosx = 0.;
87 fCosy = 0.;
88 fCosz = 1.;
89 fPseudoRapidity = 0.;
5a881c97 90
68ca986e 91 fFermiflag = 1;
92 // LHC values for beam divergence and crossing angle
93 fBeamDiv = 0.000032;
94 fBeamCrossAngle = 0.0001;
95 fBeamCrossPlane = 2;
5a881c97 96
97 Int_t i, j;
98 for(i=0; i<201; i++){
99 fProbintp[i] = 0;
100 fProbintn[i] = 0;
101 }
102 for(j=0; j<3; j++){
103 fPp[i] = 0;
104 }
105 fDebugOpt = 0;
68ca986e 106}
107
108//_____________________________________________________________________________
109void AliGenZDC::Init()
110{
5a881c97 111 printf("\n\n AliGenZDC initialized with:\n");
866ab5a2 112 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
68ca986e 113 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
114 fBeamCrossPlane);
5a881c97 115
68ca986e 116 //Initialize Fermi momentum distributions for Pb-Pb
117 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
118}
119
120//_____________________________________________________________________________
121void AliGenZDC::Generate()
122{
123 //
124 // Generate one trigger (n or p)
125 //
c0ceba4c 126 Int_t i;
127
5a881c97 128 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
129 Float_t fPTrack[3], ptot = fPMin;
68ca986e 130 Int_t nt;
131
866ab5a2 132 if(fPseudoRapidity==0.){
68ca986e 133 pLab[0] = ptot*fCosx;
134 pLab[1] = ptot*fCosy;
135 pLab[2] = ptot*fCosz;
136 }
137 else{
138 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
139 pLab[0] = -ptot*TMath::Sin(scang);
140 pLab[1] = 0.;
141 pLab[2] = ptot*TMath::Cos(scang);
142 }
c0ceba4c 143 for(i=0; i<=2; i++){
68ca986e 144 fP[i] = pLab[i];
145 }
146
5a881c97 147
68ca986e 148 // Beam divergence and crossing angle
866ab5a2 149 if(fBeamCrossAngle!=0.) {
150 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
151 for(i=0; i<=2; i++){
152 fP[i] = pLab[i];
153 }
154 }
155 if(fBeamDiv!=0.) {
156 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
157 for(i=0; i<=2; i++){
158 fP[i] = pLab[i];
159 }
160 }
161
68ca986e 162 // If required apply the Fermi momentum
163 if(fFermiflag==1){
164 if((fIpart==kProton) || (fIpart==kNeutron)){
165 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
166 }
5a881c97 167 Mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
168 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+Mass*Mass);
c0ceba4c 169 for(i=0; i<=2; i++){
68ca986e 170 dddp[i] = ddp[i];
171 }
5a881c97 172 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass);
68ca986e 173
866ab5a2 174 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
68ca986e 175 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
176
68ca986e 177 pFermi.Boost(b);
c0ceba4c 178 for(i=0; i<=2; i++){
68ca986e 179 fBoostP[i] = pFermi[i];
866ab5a2 180 fP[i] = pFermi[i];
68ca986e 181 }
182
183 }
866ab5a2 184
185 for(i=0; i<=2; i++){
186 fPTrack[i] = fP[i];
187 }
188
68ca986e 189 Float_t polar[3] = {0,0,0};
866ab5a2 190 gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
1de555dc 191 kPPrimary,nt);
5a881c97 192 if(fDebugOpt == 1){
193 printf("\n\n Track momentum:\n");
194 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
195 }
68ca986e 196}
197
198//_____________________________________________________________________________
5a881c97 199void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp,
200 Double_t *fProbintp, Double_t *fProbintn)
68ca986e 201{
202//
203// Momenta distributions according to the "double-gaussian"
204// distribution (Ilinov) - equal for protons and neutrons
205//
5a881c97 206
68ca986e 207 fProbintp[0] = 0;
208 fProbintn[0] = 0;
209 Double_t sig1 = 0.113;
210 Double_t sig2 = 0.250;
211 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
212 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
213
214 for(Int_t i=1; i<=200; i++){
215 Double_t p = i*0.005;
216 fPp[i] = p;
68ca986e 217 Double_t e1 = (p*p)/(2.*sig1*sig1);
218 Double_t e2 = (p*p)/(2.*sig2*sig2);
219 Double_t f1 = TMath::Exp(-(e1));
220 Double_t f2 = TMath::Exp(-(e2));
221 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
222 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
68ca986e 223 fProbintp[i] = fProbintp[i-1] + probp;
224 fProbintn[i] = fProbintp[i];
5a881c97 225 }
226 if(fDebugOpt == 1){
227 printf("\n\n Initialization of Fermi momenta distribution \n");
228 for(Int_t i=0; i<=200; i++){
229 printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
230 }
68ca986e 231 }
232}
233//_____________________________________________________________________________
5a881c97 234void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
235 Double_t *fProbintn, Double_t *ddp)
68ca986e 236{
237//
238// Compute Fermi momentum for spectator nucleons
239//
5a881c97 240
68ca986e 241 Int_t i;
242 Float_t xx = gRandom->Rndm();
699b37ac 243 assert ( id==kProton || id==kNeutron );
68ca986e 244 if(id==kProton){
0ff3ad02 245 for(i=1; i<=200; i++){
68ca986e 246 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
247 }
248 }
94de3818 249 else {
68ca986e 250 for(i=0; i<=200; i++){
251 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
252 }
253 }
254 Float_t pext = fPp[i]+0.001;
255 Float_t phi = k2PI*(gRandom->Rndm());
256 Float_t cost = (1.-2.*(gRandom->Rndm()));
257 Float_t tet = TMath::ACos(cost);
258 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
259 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
260 ddp[2] = pext*cost;
5a881c97 261
262 if(fDebugOpt == 1){
263 printf("\n\n Extraction of Fermi momentum\n");
264 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
265 }
68ca986e 266}
267
268//_____________________________________________________________________________
269void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
5a881c97 270 Int_t fBeamCrossPlane, Double_t *pLab)
68ca986e 271{
866ab5a2 272 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
68ca986e 273 Double_t rvec;
c0ceba4c 274
275 Int_t i;
68ca986e 276 Double_t pmq = 0.;
c0ceba4c 277 for(i=0; i<=2; i++){
68ca986e 278 pmq = pmq+pLab[i]*pLab[i];
279 }
280 Double_t pmod = TMath::Sqrt(pmq);
68ca986e 281
68ca986e 282 if(icross==0){
283 rvec = gRandom->Gaus(0.0,1.0);
284 tetdiv = fBeamDiv * TMath::Abs(rvec);
285 fidiv = (gRandom->Rndm())*k2PI;
286 }
287 else if(icross==1){
288 if(fBeamCrossPlane==0.){
289 tetdiv = 0.;
290 fidiv = 0.;
291 }
292 else if(fBeamCrossPlane==1.){
293 tetdiv = fBeamCrossAngle;
294 fidiv = 0.;
295 }
296 else if(fBeamCrossPlane==2.){
297 tetdiv = fBeamCrossAngle;
736c9b58 298 fidiv = k2PI/4.;
68ca986e 299 }
300 }
866ab5a2 301
302 tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]);
303 if(pLab[1]!=0. || pLab[0]!=0.){
304 fipart = TMath::ATan2(pLab[1],pLab[0]);
68ca986e 305 }
306 else{
307 fipart = 0.;
308 }
309 if(fipart<0.) {fipart = fipart+k2PI;}
68ca986e 310 tetdiv = tetdiv*kRaddeg;
311 fidiv = fidiv*kRaddeg;
312 tetpart = tetpart*kRaddeg;
313 fipart = fipart*kRaddeg;
314 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
315 tetsum = angleSum[0];
316 fisum = angleSum[1];
68ca986e 317 tetsum = tetsum*kDegrad;
318 fisum = fisum*kDegrad;
319 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
320 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
321 pLab[2] = pmod*TMath::Cos(tetsum);
5a881c97 322 if(fDebugOpt == 1){
323 printf("\n\n Beam divergence and crossing angle\n");
324 for(i=0; i<=2; i++){
325 printf(" pLab[%d] = %f\n",i,pLab[i]);
326 }
68ca986e 327 }
328}
329
330//_____________________________________________________________________________
331void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
5a881c97 332 Double_t phi2, Double_t *angleSum)
68ca986e 333{
334 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
335 Double_t rtetsum, tetsum, fisum;
336
337 temp = -1.;
338 conv = 180./TMath::ACos(temp);
339
340 ct1 = TMath::Cos(theta1/conv);
341 st1 = TMath::Sin(theta1/conv);
342 cp1 = TMath::Cos(phi1/conv);
343 sp1 = TMath::Sin(phi1/conv);
344 ct2 = TMath::Cos(theta2/conv);
345 st2 = TMath::Sin(theta2/conv);
346 cp2 = TMath::Cos(phi2/conv);
347 sp2 = TMath::Sin(phi2/conv);
348 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
349 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
350 cz = ct1*ct2-st1*st2*cp2;
351
352 rtetsum = TMath::ACos(cz);
353 tetsum = conv*rtetsum;
354 if(tetsum==0. || tetsum==180.){
355 fisum = 0.;
356 return;
357 }
358 temp = cx/TMath::Sin(rtetsum);
359 if(temp>1.) temp=1.;
360 if(temp<-1.) temp=-1.;
361 fisum = conv*TMath::ACos(temp);
362 if(cy<0) {fisum = 360.-fisum;}
68ca986e 363 angleSum[0] = tetsum;
364 angleSum[1] = fisum;
365}
366