1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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 **************************************************************************/
18 Revision 1.8 2001/04/20 10:10:25 coppedis
21 Revision 1.7 2001/03/15 16:13:28 coppedis
24 Revision 1.6 2000/11/30 17:16:14 coppedis
25 Changes suggested by fca
27 Revision 1.5 2000/11/22 11:30:12 coppedis
30 Revision 1.4 2000/10/05 08:02:47 fca
31 Correction of the generator direction
33 Revision 1.3 2000/10/02 21:28:20 fca
34 Removal of useless dependecies via forward declarations
36 Revision 1.2 2000/07/11 11:12:34 fca
37 Some syntax corrections for non standard HP aCC
39 Revision 1.1 2000/07/10 13:58:01 fca
40 New version of ZDC from E.Scomparin & C.Oppedisano
42 Revision 1.7 2000/01/19 17:17:40 fca
44 Revision 1.6 1999/09/29 09:24:35 fca
45 Introduction of the Copyright and cvs Log
51 #include <TLorentzVector.h>
53 #include "TDatabasePDG.h"
55 #include "AliGenZDC.h"
59 #include "AliMCProcess.h"
63 //_____________________________________________________________________________
64 AliGenZDC::AliGenZDC()
68 // Default constructor
73 //_____________________________________________________________________________
74 AliGenZDC::AliGenZDC(Int_t npart)
78 // Standard constructor
81 fTitle = "Generation of Test Particles for ZDCs";
89 // LHC values for beam divergence and crossing angle
91 fBeamCrossAngle = 0.0001;
105 //_____________________________________________________________________________
106 void AliGenZDC::Init()
108 printf("\n\n AliGenZDC initialized with:\n");
109 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
110 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
113 //Initialize Fermi momentum distributions for Pb-Pb
114 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
117 //_____________________________________________________________________________
118 void AliGenZDC::Generate()
121 // Generate one trigger (n or p)
125 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
126 Float_t fPTrack[3], ptot = fPMin;
129 if(fPseudoRapidity==0.){
130 pLab[0] = ptot*fCosx;
131 pLab[1] = ptot*fCosy;
132 pLab[2] = ptot*fCosz;
135 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
136 pLab[0] = -ptot*TMath::Sin(scang);
138 pLab[2] = ptot*TMath::Cos(scang);
145 // Beam divergence and crossing angle
146 if(fBeamCrossAngle!=0.) {
147 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
153 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
159 // If required apply the Fermi momentum
161 if((fIpart==kProton) || (fIpart==kNeutron)){
162 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
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);
169 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass);
171 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
172 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
176 fBoostP[i] = pFermi[i];
186 Float_t polar[3] = {0,0,0};
187 gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
190 printf("\n\n Track momentum:\n");
191 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
195 //_____________________________________________________________________________
196 void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp,
197 Double_t *fProbintp, Double_t *fProbintn)
200 // Momenta distributions according to the "double-gaussian"
201 // distribution (Ilinov) - equal for protons and neutrons
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)));
211 for(Int_t i=1; i<=200; i++){
212 Double_t p = i*0.005;
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;
220 fProbintp[i] = fProbintp[i-1] + probp;
221 fProbintn[i] = fProbintp[i];
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]);
230 //_____________________________________________________________________________
231 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
232 Double_t *fProbintn, Double_t *ddp)
235 // Compute Fermi momentum for spectator nucleons
239 Float_t xx = gRandom->Rndm();
240 assert ( id==kProton || id==kNeutron );
242 for(i=0; i<=200; i++){
243 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
247 for(i=0; i<=200; i++){
248 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
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);
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]);
265 //_____________________________________________________________________________
266 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
267 Int_t fBeamCrossPlane, Double_t *pLab)
269 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
275 pmq = pmq+pLab[i]*pLab[i];
277 Double_t pmod = TMath::Sqrt(pmq);
280 rvec = gRandom->Gaus(0.0,1.0);
281 tetdiv = fBeamDiv * TMath::Abs(rvec);
282 fidiv = (gRandom->Rndm())*k2PI;
285 if(fBeamCrossPlane==0.){
289 else if(fBeamCrossPlane==1.){
290 tetdiv = fBeamCrossAngle;
293 else if(fBeamCrossPlane==2.){
294 tetdiv = fBeamCrossAngle;
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]);
306 if(fipart<0.) {fipart = fipart+k2PI;}
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];
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);
320 printf("\n\n Beam divergence and crossing angle\n");
322 printf(" pLab[%d] = %f\n",i,pLab[i]);
327 //_____________________________________________________________________________
328 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
329 Double_t phi2, Double_t *angleSum)
331 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
332 Double_t rtetsum, tetsum, fisum;
335 conv = 180./TMath::ACos(temp);
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;
349 rtetsum = TMath::ACos(cz);
350 tetsum = conv*rtetsum;
351 if(tetsum==0. || tetsum==180.){
355 temp = cx/TMath::Sin(rtetsum);
357 if(temp<-1.) temp=-1.;
358 fisum = conv*TMath::ACos(temp);
359 if(cy<0) {fisum = 360.-fisum;}
360 angleSum[0] = tetsum;