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"
33 //_____________________________________________________________________________
34 AliGenZDC::AliGenZDC()
38 // Default constructor
43 //_____________________________________________________________________________
44 AliGenZDC::AliGenZDC(Int_t npart)
48 // Standard constructor
51 fTitle = "Generation of Test Particles for ZDCs";
59 // LHC values for beam divergence and crossing angle
61 fBeamCrossAngle = 0.0001;
75 //_____________________________________________________________________________
76 void AliGenZDC::Init()
78 printf("\n\n AliGenZDC initialized with:\n");
79 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
80 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
83 //Initialize Fermi momentum distributions for Pb-Pb
84 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
87 //_____________________________________________________________________________
88 void AliGenZDC::Generate()
91 // Generate one trigger (n or p)
95 Double_t Mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
96 Float_t fPTrack[3], ptot = fPMin;
99 if(fPseudoRapidity==0.){
100 pLab[0] = ptot*fCosx;
101 pLab[1] = ptot*fCosy;
102 pLab[2] = ptot*fCosz;
105 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
106 pLab[0] = -ptot*TMath::Sin(scang);
108 pLab[2] = ptot*TMath::Cos(scang);
115 // Beam divergence and crossing angle
116 if(fBeamCrossAngle!=0.) {
117 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
123 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
129 // If required apply the Fermi momentum
131 if((fIpart==kProton) || (fIpart==kNeutron)){
132 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
134 Mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
135 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+Mass*Mass);
139 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+Mass*Mass);
141 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
142 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
146 fBoostP[i] = pFermi[i];
156 Float_t polar[3] = {0,0,0};
157 gAlice->SetTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
160 printf("\n\n Track momentum:\n");
161 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
165 //_____________________________________________________________________________
166 void AliGenZDC::FermiTwoGaussian(Float_t A, Float_t Z, Double_t *fPp,
167 Double_t *fProbintp, Double_t *fProbintn)
170 // Momenta distributions according to the "double-gaussian"
171 // distribution (Ilinov) - equal for protons and neutrons
176 Double_t sig1 = 0.113;
177 Double_t sig2 = 0.250;
178 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
179 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
181 for(Int_t i=1; i<=200; i++){
182 Double_t p = i*0.005;
184 Double_t e1 = (p*p)/(2.*sig1*sig1);
185 Double_t e2 = (p*p)/(2.*sig2*sig2);
186 Double_t f1 = TMath::Exp(-(e1));
187 Double_t f2 = TMath::Exp(-(e2));
188 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
189 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
190 fProbintp[i] = fProbintp[i-1] + probp;
191 fProbintn[i] = fProbintp[i];
194 printf("\n\n Initialization of Fermi momenta distribution \n");
195 for(Int_t i=0; i<=200; i++){
196 printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
200 //_____________________________________________________________________________
201 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
202 Double_t *fProbintn, Double_t *ddp)
205 // Compute Fermi momentum for spectator nucleons
209 Float_t xx = gRandom->Rndm();
210 assert ( id==kProton || id==kNeutron );
212 for(i=1; i<=200; i++){
213 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
217 for(i=0; i<=200; i++){
218 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
221 Float_t pext = fPp[i]+0.001;
222 Float_t phi = k2PI*(gRandom->Rndm());
223 Float_t cost = (1.-2.*(gRandom->Rndm()));
224 Float_t tet = TMath::ACos(cost);
225 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
226 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
230 printf("\n\n Extraction of Fermi momentum\n");
231 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
235 //_____________________________________________________________________________
236 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
237 Int_t fBeamCrossPlane, Double_t *pLab)
239 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
245 pmq = pmq+pLab[i]*pLab[i];
247 Double_t pmod = TMath::Sqrt(pmq);
250 rvec = gRandom->Gaus(0.0,1.0);
251 tetdiv = fBeamDiv * TMath::Abs(rvec);
252 fidiv = (gRandom->Rndm())*k2PI;
255 if(fBeamCrossPlane==0.){
259 else if(fBeamCrossPlane==1.){
260 tetdiv = fBeamCrossAngle;
263 else if(fBeamCrossPlane==2.){
264 tetdiv = fBeamCrossAngle;
269 tetpart = TMath::ATan(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1])/pLab[2]);
270 if(pLab[1]!=0. || pLab[0]!=0.){
271 fipart = TMath::ATan2(pLab[1],pLab[0]);
276 if(fipart<0.) {fipart = fipart+k2PI;}
277 tetdiv = tetdiv*kRaddeg;
278 fidiv = fidiv*kRaddeg;
279 tetpart = tetpart*kRaddeg;
280 fipart = fipart*kRaddeg;
281 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
282 tetsum = angleSum[0];
284 tetsum = tetsum*kDegrad;
285 fisum = fisum*kDegrad;
286 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
287 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
288 pLab[2] = pmod*TMath::Cos(tetsum);
290 printf("\n\n Beam divergence and crossing angle\n");
292 printf(" pLab[%d] = %f\n",i,pLab[i]);
297 //_____________________________________________________________________________
298 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
299 Double_t phi2, Double_t *angleSum)
301 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
302 Double_t rtetsum, tetsum, fisum;
305 conv = 180./TMath::ACos(temp);
307 ct1 = TMath::Cos(theta1/conv);
308 st1 = TMath::Sin(theta1/conv);
309 cp1 = TMath::Cos(phi1/conv);
310 sp1 = TMath::Sin(phi1/conv);
311 ct2 = TMath::Cos(theta2/conv);
312 st2 = TMath::Sin(theta2/conv);
313 cp2 = TMath::Cos(phi2/conv);
314 sp2 = TMath::Sin(phi2/conv);
315 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
316 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
317 cz = ct1*ct2-st1*st2*cp2;
319 rtetsum = TMath::ACos(cz);
320 tetsum = conv*rtetsum;
321 if(tetsum==0. || tetsum==180.){
325 temp = cx/TMath::Sin(rtetsum);
327 if(temp<-1.) temp=-1.;
328 fisum = conv*TMath::ACos(temp);
329 if(cy<0) {fisum = 360.-fisum;}
330 angleSum[0] = tetsum;