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 //////////////////////////////////////////////////////////////////////
20 // Generator of spectator nucleons (either protons or neutrons)//
21 // computes beam crossing and divergence and Fermi momentum //
23 /////////////////////////////////////////////////////////////////////
27 #include <TDatabasePDG.h>
28 #include <TLorentzVector.h>
29 #include <TMCProcess.h>
35 #include "AliGenZDC.h"
41 //_____________________________________________________________________________
42 AliGenZDC::AliGenZDC()
46 // Default constructor
51 //_____________________________________________________________________________
52 AliGenZDC::AliGenZDC(Int_t npart)
56 // Standard constructor
59 fTitle = "Generation of Test Particles for ZDCs";
67 // LHC values for beam divergence and crossing angle
69 fBeamCrossAngle = 0.0001;
77 for(j=0; j<3; j++) fPp[i] = 0;
81 //_____________________________________________________________________________
82 void AliGenZDC::Init()
84 //Initialize Fermi momentum distributions for Pb-Pb
86 printf("\n\n AliGenZDC initialization:\n");
87 printf(" Particle: %d, Track cosines: x = %f, y = %f, z = %f \n",
88 fIpart,fCosx,fCosy,fCosz);
89 printf(" Fermi flag = %d, Beam divergence = %f, Crossing angle "
90 "= %f, Crossing plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
93 FermiTwoGaussian(207.,fPp,fProbintp,fProbintn);
96 //_____________________________________________________________________________
97 void AliGenZDC::Generate()
100 // Generate one trigger (n or p)
104 Double_t mass, pLab[3], fP0, fP[3], fBoostP[3], ddp[3], dddp0, dddp[3];
105 Float_t fPTrack[3], ptot = fPMin;
108 if(fPseudoRapidity==0.){
109 pLab[0] = ptot*fCosx;
110 pLab[1] = ptot*fCosy;
111 pLab[2] = ptot*fCosz;
114 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
115 pLab[0] = -ptot*TMath::Sin(scang);
117 pLab[2] = ptot*TMath::Cos(scang);
119 for(i=0; i<=2; i++) fP[i] = pLab[i];
121 printf("\n\n Particle momentum before divergence and crossing\n");
122 for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]);
125 // Beam divergence and crossing angle
126 if(fBeamCrossAngle!=0.) {
127 BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
128 for(i=0; i<=2; i++) fP[i] = pLab[i];
131 BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);
132 for(i=0; i<=2; i++) fP[i] = pLab[i];
135 // If required apply the Fermi momentum
137 if((fIpart==kProton) || (fIpart==kNeutron))
138 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
139 mass=gAlice->PDGDB()->GetParticle(fIpart)->Mass();
140 fP0 = TMath::Sqrt(fP[0]*fP[0]+fP[1]*fP[1]+fP[2]*fP[2]+mass*mass);
141 for(i=0; i<=2; i++) dddp[i] = ddp[i];
142 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass);
144 TVector3 b(fP[0]/fP0, fP[1]/fP0, fP[2]/fP0);
145 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
149 fBoostP[i] = pFermi[i];
155 for(i=0; i<=2; i++) fPTrack[i] = fP[i];
157 Float_t polar[3] = {0,0,0};
158 gAlice->GetMCApp()->PushTrack(fTrackIt,-1,fIpart,fPTrack,fOrigin.GetArray(),polar,0,
160 // -----------------------------------------------------------------------
162 printf("\n\n Track momentum:\n");
163 printf("\n fPTrack = %f, %f, %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
165 else if(fDebugOpt == 2){
167 if((file = fopen("SpectMomentum.dat","a")) == NULL){
168 printf("Cannot open file SpectMomentum.dat\n");
171 fprintf(file," %f \t %f \t %f \n",fPTrack[0],fPTrack[1],fPTrack[2]);
177 //_____________________________________________________________________________
178 void AliGenZDC::FermiTwoGaussian(Float_t A, Double_t *fPp,
179 Double_t *fProbintp, Double_t *fProbintn)
182 // Momenta distributions according to the "double-gaussian"
183 // distribution (Ilinov) - equal for protons and neutrons
188 Double_t sig1 = 0.113;
189 Double_t sig2 = 0.250;
190 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
191 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
193 for(Int_t i=1; i<=200; i++){
194 Double_t p = i*0.005;
196 Double_t e1 = (p*p)/(2.*sig1*sig1);
197 Double_t e2 = (p*p)/(2.*sig2*sig2);
198 Double_t f1 = TMath::Exp(-(e1));
199 Double_t f2 = TMath::Exp(-(e2));
200 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
201 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
202 fProbintp[i] = fProbintp[i-1] + probp;
203 fProbintn[i] = fProbintp[i];
206 printf("\n\n Initialization of Fermi momenta distribution \n");
207 //for(Int_t i=0; i<=200; i++)
208 // printf(" fProbintp[%d] = %f, fProbintn[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
211 //_____________________________________________________________________________
212 void AliGenZDC::ExtractFermi(Int_t id, Double_t *fPp, Double_t *fProbintp,
213 Double_t *fProbintn, Double_t *ddp)
216 // Compute Fermi momentum for spectator nucleons
220 Float_t xx = gRandom->Rndm();
221 assert ( id==kProton || id==kNeutron );
223 for(i=1; i<=200; i++){
224 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
228 for(i=0; i<=200; i++){
229 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
232 Float_t pext = fPp[i]+0.001;
233 Float_t phi = k2PI*(gRandom->Rndm());
234 Float_t cost = (1.-2.*(gRandom->Rndm()));
235 Float_t tet = TMath::ACos(cost);
236 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
237 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
241 printf("\n\n Extraction of Fermi momentum\n");
242 printf("\n pxFermi = %f pyFermi = %f pzFermi = %f \n",ddp[0],ddp[1],ddp[2]);
246 //_____________________________________________________________________________
247 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
248 Int_t fBeamCrossPlane, Double_t *pLab)
250 // Applying beam divergence and crossing angle
252 Double_t tetpart, fipart, tetdiv=0, fidiv=0, angleSum[2], tetsum, fisum;
257 for(i=0; i<=2; i++) pmq = pmq+pLab[i]*pLab[i];
258 Double_t pmod = TMath::Sqrt(pmq);
260 if(icross==0){ // ##### Beam divergence
261 rvec = gRandom->Gaus(0.0,1.0);
262 tetdiv = fBeamDiv * TMath::Abs(rvec);
263 fidiv = (gRandom->Rndm())*k2PI;
265 else if(icross==1){ // ##### Crossing angle
266 if(fBeamCrossPlane==0.){
270 else if(fBeamCrossPlane==1.){ // Horizontal crossing plane
271 tetdiv = fBeamCrossAngle;
274 else if(fBeamCrossPlane==2.){ // Vertical crossing plane
275 tetdiv = fBeamCrossAngle;
280 tetpart = TMath::ATan2(TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]),pLab[2]);
281 if(pLab[1]!=0. || pLab[0]!=0.) fipart = TMath::ATan2(pLab[1],pLab[0]);
283 if(fipart<0.) {fipart = fipart+k2PI;}
284 tetdiv = tetdiv*kRaddeg;
285 fidiv = fidiv*kRaddeg;
286 tetpart = tetpart*kRaddeg;
287 fipart = fipart*kRaddeg;
288 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
289 tetsum = angleSum[0];
291 tetsum = tetsum*kDegrad;
292 fisum = fisum*kDegrad;
293 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
294 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
295 pLab[2] = pmod*TMath::Cos(tetsum);
297 if(icross==0) printf("\n\n Beam divergence \n");
298 else printf("\n\n Beam crossing \n");
299 for(i=0; i<=2; i++)printf(" pLab[%d] = %f\n",i,pLab[i]);
303 //_____________________________________________________________________________
304 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
305 Double_t phi2, Double_t *angleSum)
307 // Calculating the sum of 2 angles
308 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
309 Double_t rtetsum, tetsum, fisum;
312 conv = 180./TMath::ACos(temp);
314 ct1 = TMath::Cos(theta1/conv);
315 st1 = TMath::Sin(theta1/conv);
316 cp1 = TMath::Cos(phi1/conv);
317 sp1 = TMath::Sin(phi1/conv);
318 ct2 = TMath::Cos(theta2/conv);
319 st2 = TMath::Sin(theta2/conv);
320 cp2 = TMath::Cos(phi2/conv);
321 sp2 = TMath::Sin(phi2/conv);
322 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
323 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
324 cz = ct1*ct2-st1*st2*cp2;
326 rtetsum = TMath::ACos(cz);
327 tetsum = conv*rtetsum;
328 if(tetsum==0. || tetsum==180.){
332 temp = cx/TMath::Sin(rtetsum);
334 if(temp<-1.) temp=-1.;
335 fisum = conv*TMath::ACos(temp);
336 if(cy<0) {fisum = 360.-fisum;}
337 angleSum[0] = tetsum;