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 **************************************************************************/
20 #include <TDatabasePDG.h>
21 #include <TLorentzVector.h>
22 #include <TMCProcess.h>
28 #include "AliGenZDC.h"
34 //_____________________________________________________________________________
35 AliGenZDC::AliGenZDC()
39 // Default constructor
44 //_____________________________________________________________________________
45 AliGenZDC::AliGenZDC(Int_t npart)
49 // Standard constructor
52 fTitle = "Generation of Test Particles for ZDCs";
60 // LHC values for beam divergence and crossing angle
62 fBeamCrossAngle = 0.0001;
76 //_____________________________________________________________________________
77 void AliGenZDC::Init()
79 printf("\n\n AliGenZDC initialized with:\n");
80 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
81 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
84 //Initialize Fermi momentum distributions for Pb-Pb
85 FermiTwoGaussian(207.,fPp,fProbintp,fProbintn);
88 //_____________________________________________________________________________
89 void AliGenZDC::Generate()
92 // Generate one trigger (n or p)
96 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
97 Float_t fPTrack[3], ptot = fPMin;
100 if(fPseudoRapidity==0.){
101 pLab[0] = ptot*fCosx;
102 pLab[1] = ptot*fCosy;
103 pLab[2] = ptot*fCosz;
106 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
107 pLab[0] = -ptot*TMath::Sin(scang);
109 pLab[2] = ptot*TMath::Cos(scang);
116 // Beam divergence and crossing angle
117 if(fBeamCrossAngle!=0.) {
118 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
124 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
130 // If required apply the Fermi momentum
132 if((fIpart==kProton) || (fIpart==kNeutron)){
133 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
135 Mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
136 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+Mass*Mass);
140 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass);
142 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
143 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
147 fBoostP[i] = pFermi[i];
157 Float_t polar[3] = {0,0,0};
158 gAlice->GetMCApp()->PushTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
161 printf("\n\n Track momentum:\n");
162 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
166 //_____________________________________________________________________________
167 void AliGenZDC::FermiTwoGaussian(Float_t A, Double_t *fPp,
168 Double_t *fProbintp, Double_t *fProbintn)
171 // Momenta distributions according to the "double-gaussian"
172 // distribution (Ilinov) - equal for protons and neutrons
177 Double_t sig1 = 0.113;
178 Double_t sig2 = 0.250;
179 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
180 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
182 for(Int_t i=1; i<=200; i++){
183 Double_t p = i*0.005;
185 Double_t e1 = (p*p)/(2.*sig1*sig1);
186 Double_t e2 = (p*p)/(2.*sig2*sig2);
187 Double_t f1 = TMath::Exp(-(e1));
188 Double_t f2 = TMath::Exp(-(e2));
189 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
190 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
191 fProbintp[i] = fProbintp[i-1] + probp;
192 fProbintn[i] = fProbintp[i];
195 printf("\n\n Initialization of Fermi momenta distribution \n");
196 for(Int_t i=0; i<=200; i++){
197 printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
201 //_____________________________________________________________________________
202 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
203 Double_t *fProbintn, Double_t *ddp)
206 // Compute Fermi momentum for spectator nucleons
210 Float_t xx = gRandom->Rndm();
211 assert ( id==kProton || id==kNeutron );
213 for(i=1; i<=200; i++){
214 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
218 for(i=0; i<=200; i++){
219 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
222 Float_t pext = fPp[i]+0.001;
223 Float_t phi = k2PI*(gRandom->Rndm());
224 Float_t cost = (1.-2.*(gRandom->Rndm()));
225 Float_t tet = TMath::ACos(cost);
226 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
227 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
231 printf("\n\n Extraction of Fermi momentum\n");
232 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
236 //_____________________________________________________________________________
237 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
238 Int_t fBeamCrossPlane, Double_t *pLab)
240 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
246 pmq = pmq+pLab[i]*pLab[i];
248 Double_t pmod = TMath::Sqrt(pmq);
251 rvec = gRandom->Gaus(0.0,1.0);
252 tetdiv = fBeamDiv * TMath::Abs(rvec);
253 fidiv = (gRandom->Rndm())*k2PI;
256 if(fBeamCrossPlane==0.){
260 else if(fBeamCrossPlane==1.){
261 tetdiv = fBeamCrossAngle;
264 else if(fBeamCrossPlane==2.){
265 tetdiv = fBeamCrossAngle;
270 tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]);
271 if(pLab[1]!=0. || pLab[0]!=0.){
272 fipart = TMath::ATan2(pLab[1],pLab[0]);
277 if(fipart<0.) {fipart = fipart+k2PI;}
278 tetdiv = tetdiv*kRaddeg;
279 fidiv = fidiv*kRaddeg;
280 tetpart = tetpart*kRaddeg;
281 fipart = fipart*kRaddeg;
282 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
283 tetsum = angleSum[0];
285 tetsum = tetsum*kDegrad;
286 fisum = fisum*kDegrad;
287 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
288 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
289 pLab[2] = pmod*TMath::Cos(tetsum);
291 printf("\n\n Beam divergence and crossing angle\n");
293 printf(" pLab[%d] = %f\n",i,pLab[i]);
298 //_____________________________________________________________________________
299 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
300 Double_t phi2, Double_t *angleSum)
302 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
303 Double_t rtetsum, tetsum, fisum;
306 conv = 180./TMath::ACos(temp);
308 ct1 = TMath::Cos(theta1/conv);
309 st1 = TMath::Sin(theta1/conv);
310 cp1 = TMath::Cos(phi1/conv);
311 sp1 = TMath::Sin(phi1/conv);
312 ct2 = TMath::Cos(theta2/conv);
313 st2 = TMath::Sin(theta2/conv);
314 cp2 = TMath::Cos(phi2/conv);
315 sp2 = TMath::Sin(phi2/conv);
316 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
317 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
318 cz = ct1*ct2-st1*st2*cp2;
320 rtetsum = TMath::ACos(cz);
321 tetsum = conv*rtetsum;
322 if(tetsum==0. || tetsum==180.){
326 temp = cx/TMath::Sin(rtetsum);
328 if(temp<-1.) temp=-1.;
329 fisum = conv*TMath::ACos(temp);
330 if(cy<0) {fisum = 360.-fisum;}
331 angleSum[0] = tetsum;