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 1.2 2000/07/11 11:12:34 fca
19 Some syntax corrections for non standard HP aCC
21 Revision 1.1 2000/07/10 13:58:01 fca
22 New version of ZDC from E.Scomparin & C.Oppedisano
24 Revision 1.7 2000/01/19 17:17:40 fca
26 Revision 1.6 1999/09/29 09:24:35 fca
27 Introduction of the Copyright and cvs Log
33 #include <TLorentzVector.h>
35 #include "TDatabasePDG.h"
37 #include "AliGenZDC.h"
44 //_____________________________________________________________________________
45 AliGenZDC::AliGenZDC()
49 // Default constructor
54 //_____________________________________________________________________________
55 AliGenZDC::AliGenZDC(Int_t npart)
59 // Standard constructor
62 fTitle = "Generation of Test Particles for ZDCs";
69 // LHC values for beam divergence and crossing angle
71 fBeamCrossAngle = 0.0001;
75 //_____________________________________________________________________________
76 void AliGenZDC::Init()
78 printf(" Initializing AliGenZDC\n");
79 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
80 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
82 //Initialize Fermi momentum distributions for Pb-Pb
83 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
86 //_____________________________________________________________________________
87 void AliGenZDC::Generate()
90 // Generate one trigger (n or p)
94 Double_t mass, pLab[3], balp0, balp[3], ddp[3], dddp0, dddp[3];
98 if(fPseudoRapidity==0.){
100 pLab[1] = ptot*fCosy;
101 pLab[2] = ptot*fCosz;
104 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
105 pLab[0] = -ptot*TMath::Sin(scang);
107 pLab[2] = ptot*TMath::Cos(scang);
113 // Beam divergence and crossing angle
114 if(fBeamDiv!=0.) {BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
115 if(fBeamCrossAngle!=0.) {BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
117 // If required apply the Fermi momentum
119 if((fIpart==kProton) || (fIpart==kNeutron)){
120 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
122 mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
123 // printf(" pLABx = %f pLABy = %f pLABz = %f \n",pLab[0],pLab[1],pLab[2]);
127 balp0 = TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]+pLab[2]*pLab[2]+mass*mass);
131 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass);
133 TVector3 b(balp[0]/balp0, balp[1]/balp0, balp[2]/balp0);
134 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
136 // printf(" pmu -> pLABx = %f pLABy = %f pLABz = %f E = %f\n",
137 // balp[0],balp[1],balp[2],balp0);
138 // printf(" Beta -> bx = %f by = %f bz = %f\n", b[0], b[1], b[2]);
139 // printf(" pFermi -> px = %f, py = %f, pz = %f\n", pFermi[0], pFermi[1], pFermi[2]);
143 // printf(" Boosted momentum -> px = %f, py = %f, pz = %f\n",
144 // pFermi[0], pFermi[1], pFermi[2]);
146 fBoostP[i] = pFermi[i];
151 Float_t polar[3] = {0,0,0};
152 gAlice->SetTrack(fTrackIt,-1,fIpart,fBoostP,fOrigin.GetArray(),polar,0,
156 //_____________________________________________________________________________
157 void AliGenZDC::FermiTwoGaussian(Double_t A, Float_t Z, Double_t* fPp, Double_t*
158 fProbintp, Double_t* fProbintn)
161 // Momenta distributions according to the "double-gaussian"
162 // distribution (Ilinov) - equal for protons and neutrons
164 // printf(" Initialization of Fermi momenta distribution\n");
167 Double_t sig1 = 0.113;
168 Double_t sig2 = 0.250;
169 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
170 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
172 for(Int_t i=1; i<=200; i++){
173 Double_t p = i*0.005;
175 // printf(" fPp[%d] = %f\n",i,fPp[i]);
176 Double_t e1 = (p*p)/(2.*sig1*sig1);
177 Double_t e2 = (p*p)/(2.*sig2*sig2);
178 Double_t f1 = TMath::Exp(-(e1));
179 Double_t f2 = TMath::Exp(-(e2));
180 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
181 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
182 // printf(" probp = %f\n",probp);
183 fProbintp[i] = fProbintp[i-1] + probp;
184 fProbintn[i] = fProbintp[i];
185 // printf(" fProbintp[%d] = %f, fProbintp[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
188 //_____________________________________________________________________________
189 void AliGenZDC::ExtractFermi(Int_t id, Double_t* fPp, Double_t* fProbintp,
190 Double_t* fProbintn, Double_t* ddp)
193 // Compute Fermi momentum for spectator nucleons
196 Float_t xx = gRandom->Rndm();
197 assert ( id==kProton && id==kNeutron );
199 for(i=0; i<=200; i++){
200 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
204 for(i=0; i<=200; i++){
205 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
208 Float_t pext = fPp[i]+0.001;
209 Float_t phi = k2PI*(gRandom->Rndm());
210 Float_t cost = (1.-2.*(gRandom->Rndm()));
211 Float_t tet = TMath::ACos(cost);
212 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
213 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
217 //_____________________________________________________________________________
218 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
219 Int_t fBeamCrossPlane, Double_t* pLab)
221 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum, dplab[3];
229 pmq = pmq+pLab[i]*pLab[i];
231 Double_t pmod = TMath::Sqrt(pmq);
232 // printf(" pmod = %f\n",pmod);
234 // printf(" icross = %d, fBeamDiv = %f\n",icross,fBeamDiv);
236 rvec = gRandom->Gaus(0.0,1.0);
237 tetdiv = fBeamDiv * TMath::Abs(rvec);
238 fidiv = (gRandom->Rndm())*k2PI;
241 if(fBeamCrossPlane==0.){
245 else if(fBeamCrossPlane==1.){
246 tetdiv = fBeamCrossAngle;
249 else if(fBeamCrossPlane==2.){
250 tetdiv = fBeamCrossAngle;
254 // printf(" tetdiv = %f, fidiv = %f\n",tetdiv,fidiv);
255 tetpart = TMath::ATan(TMath::Sqrt(dplab[0]*dplab[0]+dplab[1]*dplab[1])/dplab[2]);
256 if(dplab[1]!=0. || dplab[0]!=0.){
257 fipart = TMath::ATan2(dplab[1],dplab[0]);
262 if(fipart<0.) {fipart = fipart+k2PI;}
263 // printf(" tetpart = %f, fipart = %f\n",tetpart,fipart);
264 tetdiv = tetdiv*kRaddeg;
265 fidiv = fidiv*kRaddeg;
266 tetpart = tetpart*kRaddeg;
267 fipart = fipart*kRaddeg;
268 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
269 tetsum = angleSum[0];
271 // printf(" tetsum = %f, fisum = %f\n",tetsum,fisum);
272 tetsum = tetsum*kDegrad;
273 fisum = fisum*kDegrad;
274 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
275 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
276 pLab[2] = pmod*TMath::Cos(tetsum);
277 // printf(" pLab[0] = %f pLab[1] = %f pLab[2] = %f \n\n",
278 // pLab[0],pLab[1],pLab[2]);
284 //_____________________________________________________________________________
285 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
286 Double_t phi2, Double_t* angleSum)
288 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
289 Double_t rtetsum, tetsum, fisum;
292 conv = 180./TMath::ACos(temp);
294 ct1 = TMath::Cos(theta1/conv);
295 st1 = TMath::Sin(theta1/conv);
296 cp1 = TMath::Cos(phi1/conv);
297 sp1 = TMath::Sin(phi1/conv);
298 ct2 = TMath::Cos(theta2/conv);
299 st2 = TMath::Sin(theta2/conv);
300 cp2 = TMath::Cos(phi2/conv);
301 sp2 = TMath::Sin(phi2/conv);
302 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
303 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
304 cz = ct1*ct2-st1*st2*cp2;
306 rtetsum = TMath::ACos(cz);
307 tetsum = conv*rtetsum;
308 if(tetsum==0. || tetsum==180.){
312 temp = cx/TMath::Sin(rtetsum);
314 if(temp<-1.) temp=-1.;
315 fisum = conv*TMath::ACos(temp);
316 if(cy<0) {fisum = 360.-fisum;}
317 // printf(" AddAngle -> tetsum = %f, fisum = %f\n",tetsum, fisum);
318 angleSum[0] = tetsum;