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 1.3 2000/10/02 21:28:20 fca
19 Removal of useless dependecies via forward declarations
21 Revision 1.2 2000/07/11 11:12:34 fca
22 Some syntax corrections for non standard HP aCC
24 Revision 1.1 2000/07/10 13:58:01 fca
25 New version of ZDC from E.Scomparin & C.Oppedisano
27 Revision 1.7 2000/01/19 17:17:40 fca
29 Revision 1.6 1999/09/29 09:24:35 fca
30 Introduction of the Copyright and cvs Log
36 #include <TLorentzVector.h>
38 #include "TDatabasePDG.h"
40 #include "AliGenZDC.h"
47 //_____________________________________________________________________________
48 AliGenZDC::AliGenZDC()
52 // Default constructor
57 //_____________________________________________________________________________
58 AliGenZDC::AliGenZDC(Int_t npart)
62 // Standard constructor
65 fTitle = "Generation of Test Particles for ZDCs";
72 // LHC values for beam divergence and crossing angle
74 fBeamCrossAngle = 0.0001;
78 //_____________________________________________________________________________
79 void AliGenZDC::Init()
81 printf(" Initializing AliGenZDC\n");
82 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
83 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
85 //Initialize Fermi momentum distributions for Pb-Pb
86 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
89 //_____________________________________________________________________________
90 void AliGenZDC::Generate()
93 // Generate one trigger (n or p)
97 Double_t mass, pLab[3], balp0, balp[3], ddp[3], dddp0, dddp[3];
101 if(fPseudoRapidity==0.){
102 pLab[0] = ptot*fCosx;
103 pLab[1] = ptot*fCosy;
104 pLab[2] = ptot*fCosz;
107 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
108 pLab[0] = -ptot*TMath::Sin(scang);
110 pLab[2] = ptot*TMath::Cos(scang);
116 // Beam divergence and crossing angle
117 if(fBeamDiv!=0.) {BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
118 if(fBeamCrossAngle!=0.) {BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
120 // If required apply the Fermi momentum
122 if((fIpart==kProton) || (fIpart==kNeutron)){
123 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
125 mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
126 // printf(" pLABx = %f pLABy = %f pLABz = %f \n",pLab[0],pLab[1],pLab[2]);
130 balp0 = TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]+pLab[2]*pLab[2]+mass*mass);
134 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass);
136 TVector3 b(balp[0]/balp0, balp[1]/balp0, balp[2]/balp0);
137 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
139 // printf(" pmu -> pLABx = %f pLABy = %f pLABz = %f E = %f\n",
140 // balp[0],balp[1],balp[2],balp0);
141 // printf(" Beta -> bx = %f by = %f bz = %f\n", b[0], b[1], b[2]);
142 // printf(" pFermi -> px = %f, py = %f, pz = %f\n", pFermi[0], pFermi[1], pFermi[2]);
146 // printf(" Boosted momentum -> px = %f, py = %f, pz = %f\n",
147 // pFermi[0], pFermi[1], pFermi[2]);
149 fBoostP[i] = pFermi[i];
154 Float_t polar[3] = {0,0,0};
155 fBoostP[2]=-fBoostP[2];
156 gAlice->SetTrack(fTrackIt,-1,fIpart,fBoostP,fOrigin.GetArray(),polar,0,
160 //_____________________________________________________________________________
161 void AliGenZDC::FermiTwoGaussian(Double_t A, Float_t Z, Double_t* fPp, Double_t*
162 fProbintp, Double_t* fProbintn)
165 // Momenta distributions according to the "double-gaussian"
166 // distribution (Ilinov) - equal for protons and neutrons
168 // printf(" Initialization of Fermi momenta distribution\n");
171 Double_t sig1 = 0.113;
172 Double_t sig2 = 0.250;
173 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
174 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
176 for(Int_t i=1; i<=200; i++){
177 Double_t p = i*0.005;
179 // printf(" fPp[%d] = %f\n",i,fPp[i]);
180 Double_t e1 = (p*p)/(2.*sig1*sig1);
181 Double_t e2 = (p*p)/(2.*sig2*sig2);
182 Double_t f1 = TMath::Exp(-(e1));
183 Double_t f2 = TMath::Exp(-(e2));
184 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
185 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
186 // printf(" probp = %f\n",probp);
187 fProbintp[i] = fProbintp[i-1] + probp;
188 fProbintn[i] = fProbintp[i];
189 // printf(" fProbintp[%d] = %f, fProbintp[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
192 //_____________________________________________________________________________
193 void AliGenZDC::ExtractFermi(Int_t id, Double_t* fPp, Double_t* fProbintp,
194 Double_t* fProbintn, Double_t* ddp)
197 // Compute Fermi momentum for spectator nucleons
200 Float_t xx = gRandom->Rndm();
201 assert ( id==kProton || id==kNeutron );
203 for(i=0; i<=200; i++){
204 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
208 for(i=0; i<=200; i++){
209 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
212 Float_t pext = fPp[i]+0.001;
213 Float_t phi = k2PI*(gRandom->Rndm());
214 Float_t cost = (1.-2.*(gRandom->Rndm()));
215 Float_t tet = TMath::ACos(cost);
216 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
217 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
221 //_____________________________________________________________________________
222 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
223 Int_t fBeamCrossPlane, Double_t* pLab)
225 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum, dplab[3];
233 pmq = pmq+pLab[i]*pLab[i];
235 Double_t pmod = TMath::Sqrt(pmq);
236 // printf(" pmod = %f\n",pmod);
238 // printf(" icross = %d, fBeamDiv = %f\n",icross,fBeamDiv);
240 rvec = gRandom->Gaus(0.0,1.0);
241 tetdiv = fBeamDiv * TMath::Abs(rvec);
242 fidiv = (gRandom->Rndm())*k2PI;
245 if(fBeamCrossPlane==0.){
249 else if(fBeamCrossPlane==1.){
250 tetdiv = fBeamCrossAngle;
253 else if(fBeamCrossPlane==2.){
254 tetdiv = fBeamCrossAngle;
258 // printf(" tetdiv = %f, fidiv = %f\n",tetdiv,fidiv);
259 tetpart = TMath::ATan(TMath::Sqrt(dplab[0]*dplab[0]+dplab[1]*dplab[1])/dplab[2]);
260 if(dplab[1]!=0. || dplab[0]!=0.){
261 fipart = TMath::ATan2(dplab[1],dplab[0]);
266 if(fipart<0.) {fipart = fipart+k2PI;}
267 // printf(" tetpart = %f, fipart = %f\n",tetpart,fipart);
268 tetdiv = tetdiv*kRaddeg;
269 fidiv = fidiv*kRaddeg;
270 tetpart = tetpart*kRaddeg;
271 fipart = fipart*kRaddeg;
272 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
273 tetsum = angleSum[0];
275 // printf(" tetsum = %f, fisum = %f\n",tetsum,fisum);
276 tetsum = tetsum*kDegrad;
277 fisum = fisum*kDegrad;
278 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
279 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
280 pLab[2] = pmod*TMath::Cos(tetsum);
281 // printf(" pLab[0] = %f pLab[1] = %f pLab[2] = %f \n\n",
282 // pLab[0],pLab[1],pLab[2]);
288 //_____________________________________________________________________________
289 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
290 Double_t phi2, Double_t* angleSum)
292 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
293 Double_t rtetsum, tetsum, fisum;
296 conv = 180./TMath::ACos(temp);
298 ct1 = TMath::Cos(theta1/conv);
299 st1 = TMath::Sin(theta1/conv);
300 cp1 = TMath::Cos(phi1/conv);
301 sp1 = TMath::Sin(phi1/conv);
302 ct2 = TMath::Cos(theta2/conv);
303 st2 = TMath::Sin(theta2/conv);
304 cp2 = TMath::Cos(phi2/conv);
305 sp2 = TMath::Sin(phi2/conv);
306 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
307 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
308 cz = ct1*ct2-st1*st2*cp2;
310 rtetsum = TMath::ACos(cz);
311 tetsum = conv*rtetsum;
312 if(tetsum==0. || tetsum==180.){
316 temp = cx/TMath::Sin(rtetsum);
318 if(temp<-1.) temp=-1.;
319 fisum = conv*TMath::ACos(temp);
320 if(cy<0) {fisum = 360.-fisum;}
321 // printf(" AddAngle -> tetsum = %f, fisum = %f\n",tetsum, fisum);
322 angleSum[0] = tetsum;