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 1.11 2001/11/11 17:27:50 hristov
21 Revision 1.10 2001/09/26 16:00:47 coppedis
24 Revision 1.8 2001/04/20 10:10:25 coppedis
27 Revision 1.7 2001/03/15 16:13:28 coppedis
30 Revision 1.6 2000/11/30 17:16:14 coppedis
31 Changes suggested by fca
33 Revision 1.5 2000/11/22 11:30:12 coppedis
36 Revision 1.4 2000/10/05 08:02:47 fca
37 Correction of the generator direction
39 Revision 1.3 2000/10/02 21:28:20 fca
40 Removal of useless dependecies via forward declarations
42 Revision 1.2 2000/07/11 11:12:34 fca
43 Some syntax corrections for non standard HP aCC
45 Revision 1.1 2000/07/10 13:58:01 fca
46 New version of ZDC from E.Scomparin & C.Oppedisano
48 Revision 1.7 2000/01/19 17:17:40 fca
50 Revision 1.6 1999/09/29 09:24:35 fca
51 Introduction of the Copyright and cvs Log
57 #include <TLorentzVector.h>
59 #include "TDatabasePDG.h"
60 #include "TMCProcess.h"
62 #include "AliGenZDC.h"
69 //_____________________________________________________________________________
70 AliGenZDC::AliGenZDC()
74 // Default constructor
79 //_____________________________________________________________________________
80 AliGenZDC::AliGenZDC(Int_t npart)
84 // Standard constructor
87 fTitle = "Generation of Test Particles for ZDCs";
95 // LHC values for beam divergence and crossing angle
97 fBeamCrossAngle = 0.0001;
101 for(i=0; i<201; i++){
111 //_____________________________________________________________________________
112 void AliGenZDC::Init()
114 printf("\n\n AliGenZDC initialized with:\n");
115 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
116 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
119 //Initialize Fermi momentum distributions for Pb-Pb
120 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
123 //_____________________________________________________________________________
124 void AliGenZDC::Generate()
127 // Generate one trigger (n or p)
131 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
132 Float_t fPTrack[3], ptot = fPMin;
135 if(fPseudoRapidity==0.){
136 pLab[0] = ptot*fCosx;
137 pLab[1] = ptot*fCosy;
138 pLab[2] = ptot*fCosz;
141 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
142 pLab[0] = -ptot*TMath::Sin(scang);
144 pLab[2] = ptot*TMath::Cos(scang);
151 // Beam divergence and crossing angle
152 if(fBeamCrossAngle!=0.) {
153 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
159 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
165 // If required apply the Fermi momentum
167 if((fIpart==kProton) || (fIpart==kNeutron)){
168 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
170 Mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
171 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+Mass*Mass);
175 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass);
177 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
178 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
182 fBoostP[i] = pFermi[i];
192 Float_t polar[3] = {0,0,0};
193 gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
196 printf("\n\n Track momentum:\n");
197 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
201 //_____________________________________________________________________________
202 void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp,
203 Double_t *fProbintp, Double_t *fProbintn)
206 // Momenta distributions according to the "double-gaussian"
207 // distribution (Ilinov) - equal for protons and neutrons
212 Double_t sig1 = 0.113;
213 Double_t sig2 = 0.250;
214 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
215 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
217 for(Int_t i=1; i<=200; i++){
218 Double_t p = i*0.005;
220 Double_t e1 = (p*p)/(2.*sig1*sig1);
221 Double_t e2 = (p*p)/(2.*sig2*sig2);
222 Double_t f1 = TMath::Exp(-(e1));
223 Double_t f2 = TMath::Exp(-(e2));
224 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
225 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
226 fProbintp[i] = fProbintp[i-1] + probp;
227 fProbintn[i] = fProbintp[i];
230 printf("\n\n Initialization of Fermi momenta distribution \n");
231 for(Int_t i=0; i<=200; i++){
232 printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
236 //_____________________________________________________________________________
237 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
238 Double_t *fProbintn, Double_t *ddp)
241 // Compute Fermi momentum for spectator nucleons
245 Float_t xx = gRandom->Rndm();
246 assert ( id==kProton || id==kNeutron );
248 for(i=1; i<=200; i++){
249 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
253 for(i=0; i<=200; i++){
254 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
257 Float_t pext = fPp[i]+0.001;
258 Float_t phi = k2PI*(gRandom->Rndm());
259 Float_t cost = (1.-2.*(gRandom->Rndm()));
260 Float_t tet = TMath::ACos(cost);
261 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
262 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
266 printf("\n\n Extraction of Fermi momentum\n");
267 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
271 //_____________________________________________________________________________
272 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
273 Int_t fBeamCrossPlane, Double_t *pLab)
275 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
281 pmq = pmq+pLab[i]*pLab[i];
283 Double_t pmod = TMath::Sqrt(pmq);
286 rvec = gRandom->Gaus(0.0,1.0);
287 tetdiv = fBeamDiv * TMath::Abs(rvec);
288 fidiv = (gRandom->Rndm())*k2PI;
291 if(fBeamCrossPlane==0.){
295 else if(fBeamCrossPlane==1.){
296 tetdiv = fBeamCrossAngle;
299 else if(fBeamCrossPlane==2.){
300 tetdiv = fBeamCrossAngle;
305 tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]);
306 if(pLab[1]!=0. || pLab[0]!=0.){
307 fipart = TMath::ATan2(pLab[1],pLab[0]);
312 if(fipart<0.) {fipart = fipart+k2PI;}
313 tetdiv = tetdiv*kRaddeg;
314 fidiv = fidiv*kRaddeg;
315 tetpart = tetpart*kRaddeg;
316 fipart = fipart*kRaddeg;
317 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
318 tetsum = angleSum[0];
320 tetsum = tetsum*kDegrad;
321 fisum = fisum*kDegrad;
322 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
323 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
324 pLab[2] = pmod*TMath::Cos(tetsum);
326 printf("\n\n Beam divergence and crossing angle\n");
328 printf(" pLab[%d] = %f\n",i,pLab[i]);
333 //_____________________________________________________________________________
334 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
335 Double_t phi2, Double_t *angleSum)
337 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
338 Double_t rtetsum, tetsum, fisum;
341 conv = 180./TMath::ACos(temp);
343 ct1 = TMath::Cos(theta1/conv);
344 st1 = TMath::Sin(theta1/conv);
345 cp1 = TMath::Cos(phi1/conv);
346 sp1 = TMath::Sin(phi1/conv);
347 ct2 = TMath::Cos(theta2/conv);
348 st2 = TMath::Sin(theta2/conv);
349 cp2 = TMath::Cos(phi2/conv);
350 sp2 = TMath::Sin(phi2/conv);
351 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
352 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
353 cz = ct1*ct2-st1*st2*cp2;
355 rtetsum = TMath::ACos(cz);
356 tetsum = conv*rtetsum;
357 if(tetsum==0. || tetsum==180.){
361 temp = cx/TMath::Sin(rtetsum);
363 if(temp<-1.) temp=-1.;
364 fisum = conv*TMath::ACos(temp);
365 if(cy<0) {fisum = 360.-fisum;}
366 angleSum[0] = tetsum;