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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
31ClassImp(AliGenZDC)
32
33//_____________________________________________________________________________
34AliGenZDC::AliGenZDC()
35 :AliGenerator()
36{
37 //
38 // Default constructor
39 //
40 fIpart = 0;
41}
42
43//_____________________________________________________________________________
44AliGenZDC::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//_____________________________________________________________________________
76void 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//_____________________________________________________________________________
88void 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 166void 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 201void 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//_____________________________________________________________________________
236void 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//_____________________________________________________________________________
298void 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