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 1.6 2000/11/30 17:16:14 coppedis
19 Changes suggested by fca
21 Revision 1.5 2000/11/22 11:30:12 coppedis
24 Revision 1.4 2000/10/05 08:02:47 fca
25 Correction of the generator direction
27 Revision 1.3 2000/10/02 21:28:20 fca
28 Removal of useless dependecies via forward declarations
30 Revision 1.2 2000/07/11 11:12:34 fca
31 Some syntax corrections for non standard HP aCC
33 Revision 1.1 2000/07/10 13:58:01 fca
34 New version of ZDC from E.Scomparin & C.Oppedisano
36 Revision 1.7 2000/01/19 17:17:40 fca
38 Revision 1.6 1999/09/29 09:24:35 fca
39 Introduction of the Copyright and cvs Log
45 #include <TLorentzVector.h>
47 #include "TDatabasePDG.h"
49 #include "AliGenZDC.h"
53 #include "AliMCProcess.h"
57 //_____________________________________________________________________________
58 AliGenZDC::AliGenZDC()
62 // Default constructor
67 //_____________________________________________________________________________
68 AliGenZDC::AliGenZDC(Int_t npart)
72 // Standard constructor
75 fTitle = "Generation of Test Particles for ZDCs";
83 // LHC values for beam divergence and crossing angle
85 fBeamCrossAngle = 0.0001;
99 //_____________________________________________________________________________
100 void AliGenZDC::Init()
102 printf("\n\n AliGenZDC initialized with:\n");
103 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
104 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
107 //Initialize Fermi momentum distributions for Pb-Pb
108 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
111 //_____________________________________________________________________________
112 void AliGenZDC::Generate()
115 // Generate one trigger (n or p)
119 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
120 Float_t fPTrack[3], ptot = fPMin;
123 if(fPseudoRapidity==0.){
124 pLab[0] = ptot*fCosx;
125 pLab[1] = ptot*fCosy;
126 pLab[2] = ptot*fCosz;
129 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
130 pLab[0] = -ptot*TMath::Sin(scang);
132 pLab[2] = ptot*TMath::Cos(scang);
139 printf("\n\n Initial momentum : \n");
141 printf(" p[%d] = %f\n",i,pLab[i]);
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);
178 fBoostP[i] = pFermi[i];
188 Float_t polar[3] = {0,0,0};
189 gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
192 printf("\n\n Track momentum:\n");
193 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
197 //_____________________________________________________________________________
198 void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp,
199 Double_t *fProbintp, Double_t *fProbintn)
202 // Momenta distributions according to the "double-gaussian"
203 // distribution (Ilinov) - equal for protons and neutrons
208 Double_t sig1 = 0.113;
209 Double_t sig2 = 0.250;
210 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
211 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
213 for(Int_t i=1; i<=200; i++){
214 Double_t p = i*0.005;
216 Double_t e1 = (p*p)/(2.*sig1*sig1);
217 Double_t e2 = (p*p)/(2.*sig2*sig2);
218 Double_t f1 = TMath::Exp(-(e1));
219 Double_t f2 = TMath::Exp(-(e2));
220 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
221 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
222 fProbintp[i] = fProbintp[i-1] + probp;
223 fProbintn[i] = fProbintp[i];
226 printf("\n\n Initialization of Fermi momenta distribution \n");
227 for(Int_t i=0; i<=200; i++){
228 printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
232 //_____________________________________________________________________________
233 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
234 Double_t *fProbintn, Double_t *ddp)
237 // Compute Fermi momentum for spectator nucleons
241 Float_t xx = gRandom->Rndm();
242 assert ( id==kProton || id==kNeutron );
244 for(i=0; i<=200; i++){
245 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
249 for(i=0; i<=200; i++){
250 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
253 Float_t pext = fPp[i]+0.001;
254 Float_t phi = k2PI*(gRandom->Rndm());
255 Float_t cost = (1.-2.*(gRandom->Rndm()));
256 Float_t tet = TMath::ACos(cost);
257 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
258 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
262 printf("\n\n Extraction of Fermi momentum\n");
263 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
267 //_____________________________________________________________________________
268 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
269 Int_t fBeamCrossPlane, Double_t *pLab)
271 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
277 pmq = pmq+pLab[i]*pLab[i];
279 Double_t pmod = TMath::Sqrt(pmq);
282 rvec = gRandom->Gaus(0.0,1.0);
283 tetdiv = fBeamDiv * TMath::Abs(rvec);
284 fidiv = (gRandom->Rndm())*k2PI;
287 if(fBeamCrossPlane==0.){
291 else if(fBeamCrossPlane==1.){
292 tetdiv = fBeamCrossAngle;
295 else if(fBeamCrossPlane==2.){
296 tetdiv = fBeamCrossAngle;
301 tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]);
302 if(pLab[1]!=0. || pLab[0]!=0.){
303 fipart = TMath::ATan2(pLab[1],pLab[0]);
308 if(fipart<0.) {fipart = fipart+k2PI;}
309 tetdiv = tetdiv*kRaddeg;
310 fidiv = fidiv*kRaddeg;
311 tetpart = tetpart*kRaddeg;
312 fipart = fipart*kRaddeg;
313 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
314 tetsum = angleSum[0];
316 tetsum = tetsum*kDegrad;
317 fisum = fisum*kDegrad;
318 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
319 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
320 pLab[2] = pmod*TMath::Cos(tetsum);
322 printf("\n\n Beam divergence and crossing angle\n");
324 printf(" pLab[%d] = %f\n",i,pLab[i]);
329 //_____________________________________________________________________________
330 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
331 Double_t phi2, Double_t *angleSum)
333 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
334 Double_t rtetsum, tetsum, fisum;
337 conv = 180./TMath::ACos(temp);
339 ct1 = TMath::Cos(theta1/conv);
340 st1 = TMath::Sin(theta1/conv);
341 cp1 = TMath::Cos(phi1/conv);
342 sp1 = TMath::Sin(phi1/conv);
343 ct2 = TMath::Cos(theta2/conv);
344 st2 = TMath::Sin(theta2/conv);
345 cp2 = TMath::Cos(phi2/conv);
346 sp2 = TMath::Sin(phi2/conv);
347 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
348 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
349 cz = ct1*ct2-st1*st2*cp2;
351 rtetsum = TMath::ACos(cz);
352 tetsum = conv*rtetsum;
353 if(tetsum==0. || tetsum==180.){
357 temp = cx/TMath::Sin(rtetsum);
359 if(temp<-1.) temp=-1.;
360 fisum = conv*TMath::ACos(temp);
361 if(cy<0) {fisum = 360.-fisum;}
362 angleSum[0] = tetsum;