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