Modifications needed to do the following:
[u/mrichter/AliRoot.git] / ZDC / AliGenZDC.cxx
CommitLineData
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
8a2624cc 18//////////////////////////////////////////////////////////////////////
19// // //
20// Generator of spectator nucleons (either protons or neutrons)//
21// computes beam crossing and divergence and Fermi momentum //
22// //
23/////////////////////////////////////////////////////////////////////
24
94de3818 25#include <assert.h>
26
116cbefd 27#include <TDatabasePDG.h>
68ca986e 28#include <TLorentzVector.h>
116cbefd 29#include <TMCProcess.h>
30#include <TPDGCode.h>
31#include <TRandom.h>
68ca986e 32#include <TVector3.h>
33
68ca986e 34#include "AliConst.h"
116cbefd 35#include "AliGenZDC.h"
68ca986e 36#include "AliRun.h"
5d12ce38 37#include "AliMC.h"
68ca986e 38
39ClassImp(AliGenZDC)
40
41//_____________________________________________________________________________
42AliGenZDC::AliGenZDC()
43 :AliGenerator()
44{
45 //
46 // Default constructor
47 //
48 fIpart = 0;
49}
50
51//_____________________________________________________________________________
52AliGenZDC::AliGenZDC(Int_t npart)
53 :AliGenerator(npart)
54{
55 //
56 // Standard constructor
57 //
58 fName = "AliGenZDC";
59 fTitle = "Generation of Test Particles for ZDCs";
60 fIpart = kNeutron;
61 fCosx = 0.;
62 fCosy = 0.;
63 fCosz = 1.;
64 fPseudoRapidity = 0.;
5a881c97 65
68ca986e 66 fFermiflag = 1;
67 // LHC values for beam divergence and crossing angle
68 fBeamDiv = 0.000032;
69 fBeamCrossAngle = 0.0001;
70 fBeamCrossPlane = 2;
5a881c97 71
72 Int_t i, j;
73 for(i=0; i<201; i++){
74 fProbintp[i] = 0;
75 fProbintn[i] = 0;
76 }
c294be39 77 for(j=0; j<3; j++) fPp[i] = 0;
5a881c97 78 fDebugOpt = 0;
68ca986e 79}
80
81//_____________________________________________________________________________
82void AliGenZDC::Init()
83{
8a2624cc 84 //Initialize Fermi momentum distributions for Pb-Pb
85 //
c294be39 86 printf("\n\n AliGenZDC initialization:\n");
87 printf(" Particle: %d, Track cosines: x = %f, y = %f, z = %f \n",
88 fIpart,fCosx,fCosy,fCosz);
89 printf(" Fermi flag = %d, Beam divergence = %f, Crossing angle "
90 "= %f, Crossing plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
68ca986e 91 fBeamCrossPlane);
5a881c97 92
f5cb71ad 93 FermiTwoGaussian(207.,fPp,fProbintp,fProbintn);
68ca986e 94}
95
96//_____________________________________________________________________________
97void AliGenZDC::Generate()
98{
99 //
100 // Generate one trigger (n or p)
101 //
c0ceba4c 102 Int_t i;
103
8a2624cc 104 Double_t mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
5a881c97 105 Float_t fPTrack[3], ptot = fPMin;
68ca986e 106 Int_t nt;
107
866ab5a2 108 if(fPseudoRapidity==0.){
68ca986e 109 pLab[0] = ptot*fCosx;
110 pLab[1] = ptot*fCosy;
111 pLab[2] = ptot*fCosz;
112 }
113 else{
114 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
115 pLab[0] = -ptot*TMath::Sin(scang);
116 pLab[1] = 0.;
117 pLab[2] = ptot*TMath::Cos(scang);
118 }
c294be39 119 for(i=0; i<=2; i++) fP[i] = pLab[i];
120 if(fDebugOpt == 1){
121 printf("\n\n Particle momentum before divergence and crossing\n");
122 for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]);
68ca986e 123 }
124
125 // Beam divergence and crossing angle
866ab5a2 126 if(fBeamCrossAngle!=0.) {
127 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
c294be39 128 for(i=0; i<=2; i++) fP[i] = pLab[i];
866ab5a2 129 }
130 if(fBeamDiv!=0.) {
131 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
c294be39 132 for(i=0; i<=2; i++) fP[i] = pLab[i];
866ab5a2 133 }
134
68ca986e 135 // If required apply the Fermi momentum
136 if(fFermiflag==1){
c294be39 137 if((fIpart==kProton) || (fIpart==kNeutron))
68ca986e 138 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
8a2624cc 139 mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
140 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+mass*mass);
c294be39 141 for(i=0; i<=2; i++) dddp[i] = ddp[i];
8a2624cc 142 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass);
68ca986e 143
866ab5a2 144 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
68ca986e 145 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
146
68ca986e 147 pFermi.Boost(b);
c0ceba4c 148 for(i=0; i<=2; i++){
68ca986e 149 fBoostP[i] = pFermi[i];
866ab5a2 150 fP[i] = pFermi[i];
68ca986e 151 }
152
153 }
866ab5a2 154
c294be39 155 for(i=0; i<=2; i++) fPTrack[i] = fP[i];
866ab5a2 156
68ca986e 157 Float_t polar[3] = {0,0,0};
5d12ce38 158 gAlice->GetMCApp()->PushTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
1de555dc 159 kPPrimary,nt);
03cc1ceb 160 // -----------------------------------------------------------------------
5a881c97 161 if(fDebugOpt == 1){
162 printf("\n\n Track momentum:\n");
163 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
164 }
03cc1ceb 165 else if(fDebugOpt == 2){
166 FILE *file;
167 if((file = fopen("SpectMomentum.dat","a")) == NULL){
168 printf("Cannot open file SpectMomentum.dat\n");
169 return;
170 }
171 fprintf(file," %f \t %f \t %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
172 fclose(file);
173 }
174
68ca986e 175}
176
177//_____________________________________________________________________________
f5cb71ad 178void AliGenZDC::FermiTwoGaussian(Float_t A, Double_t *fPp,
5a881c97 179 Double_t *fProbintp, Double_t *fProbintn)
68ca986e 180{
181//
182// Momenta distributions according to the "double-gaussian"
183// distribution (Ilinov) - equal for protons and neutrons
184//
5a881c97 185
68ca986e 186 fProbintp[0] = 0;
187 fProbintn[0] = 0;
188 Double_t sig1 = 0.113;
189 Double_t sig2 = 0.250;
190 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
191 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
192
193 for(Int_t i=1; i<=200; i++){
194 Double_t p = i*0.005;
195 fPp[i] = p;
68ca986e 196 Double_t e1 = (p*p)/(2.*sig1*sig1);
197 Double_t e2 = (p*p)/(2.*sig2*sig2);
198 Double_t f1 = TMath::Exp(-(e1));
199 Double_t f2 = TMath::Exp(-(e2));
200 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
201 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
68ca986e 202 fProbintp[i] = fProbintp[i-1] + probp;
203 fProbintn[i] = fProbintp[i];
5a881c97 204 }
205 if(fDebugOpt == 1){
206 printf("\n\n Initialization of Fermi momenta distribution \n");
c294be39 207 //for(Int_t i=0; i<=200; i++)
208 // printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
68ca986e 209 }
210}
211//_____________________________________________________________________________
5a881c97 212void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
213 Double_t *fProbintn, Double_t *ddp)
68ca986e 214{
215//
216// Compute Fermi momentum for spectator nucleons
217//
5a881c97 218
68ca986e 219 Int_t i;
220 Float_t xx = gRandom->Rndm();
699b37ac 221 assert ( id==kProton || id==kNeutron );
68ca986e 222 if(id==kProton){
0ff3ad02 223 for(i=1; i<=200; i++){
68ca986e 224 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
225 }
226 }
94de3818 227 else {
68ca986e 228 for(i=0; i<=200; i++){
229 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
230 }
231 }
232 Float_t pext = fPp[i]+0.001;
233 Float_t phi = k2PI*(gRandom->Rndm());
234 Float_t cost = (1.-2.*(gRandom->Rndm()));
235 Float_t tet = TMath::ACos(cost);
236 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
237 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
238 ddp[2] = pext*cost;
5a881c97 239
240 if(fDebugOpt == 1){
241 printf("\n\n Extraction of Fermi momentum\n");
242 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
243 }
68ca986e 244}
245
246//_____________________________________________________________________________
247void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
5a881c97 248 Int_t fBeamCrossPlane, Double_t *pLab)
68ca986e 249{
8a2624cc 250 // Applying beam divergence and crossing angle
251 //
866ab5a2 252 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
68ca986e 253 Double_t rvec;
c0ceba4c 254
68ca986e 255 Double_t pmq = 0.;
c294be39 256 Int_t i;
257 for(i=0; i<=2; i++) pmq = pmq+pLab[i]*pLab[i];
68ca986e 258 Double_t pmod = TMath::Sqrt(pmq);
68ca986e 259
03cc1ceb 260 if(icross==0){ // ##### Beam divergence
68ca986e 261 rvec = gRandom->Gaus(0.0,1.0);
262 tetdiv = fBeamDiv * TMath::Abs(rvec);
263 fidiv = (gRandom->Rndm())*k2PI;
264 }
03cc1ceb 265 else if(icross==1){ // ##### Crossing angle
68ca986e 266 if(fBeamCrossPlane==0.){
267 tetdiv = 0.;
268 fidiv = 0.;
269 }
03cc1ceb 270 else if(fBeamCrossPlane==1.){ // Horizontal crossing plane
68ca986e 271 tetdiv = fBeamCrossAngle;
272 fidiv = 0.;
273 }
03cc1ceb 274 else if(fBeamCrossPlane==2.){ // Vertical crossing plane
68ca986e 275 tetdiv = fBeamCrossAngle;
736c9b58 276 fidiv = k2PI/4.;
68ca986e 277 }
278 }
866ab5a2 279
03cc1ceb 280 tetpart = TMath::ATan2(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]),pLab[2]);
c294be39 281 if(pLab[1]!=0. || pLab[0]!=0.) fipart = TMath::ATan2(pLab[1],pLab[0]);
282 else fipart = 0.;
68ca986e 283 if(fipart<0.) {fipart = fipart+k2PI;}
68ca986e 284 tetdiv = tetdiv*kRaddeg;
285 fidiv = fidiv*kRaddeg;
286 tetpart = tetpart*kRaddeg;
287 fipart = fipart*kRaddeg;
288 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
289 tetsum = angleSum[0];
290 fisum = angleSum[1];
68ca986e 291 tetsum = tetsum*kDegrad;
292 fisum = fisum*kDegrad;
293 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
294 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
03cc1ceb 295 pLab[2] = pmod*TMath::Cos(tetsum);
5a881c97 296 if(fDebugOpt == 1){
03cc1ceb 297 if(icross==0) printf("\n\n Beam divergence \n");
298 else printf("\n\n Beam crossing \n");
c294be39 299 for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]);
68ca986e 300 }
301}
302
303//_____________________________________________________________________________
304void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
5a881c97 305 Double_t phi2, Double_t *angleSum)
8a2624cc 306{
307 // Calculating the sum of 2 angles
68ca986e 308 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
309 Double_t rtetsum, tetsum, fisum;
310
311 temp = -1.;
312 conv = 180./TMath::ACos(temp);
313
314 ct1 = TMath::Cos(theta1/conv);
315 st1 = TMath::Sin(theta1/conv);
316 cp1 = TMath::Cos(phi1/conv);
317 sp1 = TMath::Sin(phi1/conv);
318 ct2 = TMath::Cos(theta2/conv);
319 st2 = TMath::Sin(theta2/conv);
320 cp2 = TMath::Cos(phi2/conv);
321 sp2 = TMath::Sin(phi2/conv);
322 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
323 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
324 cz = ct1*ct2-st1*st2*cp2;
325
326 rtetsum = TMath::ACos(cz);
327 tetsum = conv*rtetsum;
328 if(tetsum==0. || tetsum==180.){
329 fisum = 0.;
330 return;
331 }
332 temp = cx/TMath::Sin(rtetsum);
333 if(temp>1.) temp=1.;
334 if(temp<-1.) temp=-1.;
335 fisum = conv*TMath::ACos(temp);
336 if(cy<0) {fisum = 360.-fisum;}
68ca986e 337 angleSum[0] = tetsum;
338 angleSum[1] = fisum;
339}
340