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 1.1 2000/07/10 13:58:01 fca
19 New version of ZDC from E.Scomparin & C.Oppedisano
21 Revision 1.7 2000/01/19 17:17:40 fca
23 Revision 1.6 1999/09/29 09:24:35 fca
24 Introduction of the Copyright and cvs Log
28 #include <TLorentzVector.h>
31 #include "AliGenZDC.h"
38 //_____________________________________________________________________________
39 AliGenZDC::AliGenZDC()
43 // Default constructor
48 //_____________________________________________________________________________
49 AliGenZDC::AliGenZDC(Int_t npart)
53 // Standard constructor
56 fTitle = "Generation of Test Particles for ZDCs";
63 // LHC values for beam divergence and crossing angle
65 fBeamCrossAngle = 0.0001;
69 //_____________________________________________________________________________
70 void AliGenZDC::Init()
72 printf(" Initializing AliGenZDC\n");
73 printf(" Fermi flag = %d, Beam Divergence = %f, Crossing Angle "
74 "= %f, Crossing Plane = %d\n\n", fFermiflag, fBeamDiv, fBeamCrossAngle,
76 //Initialize Fermi momentum distributions for Pb-Pb
77 FermiTwoGaussian(207.,82.,fPp,fProbintp,fProbintn);
80 //_____________________________________________________________________________
81 void AliGenZDC::Generate()
84 // Generate one trigger (n or p)
88 Double_t mass, pLab[3], balp0, balp[3], ddp[3], dddp0, dddp[3];
92 if(fPseudoRapidity==0.){
98 Float_t scang = 2*TMath::ATan(TMath::Exp(-(fPseudoRapidity)));
99 pLab[0] = -ptot*TMath::Sin(scang);
101 pLab[2] = ptot*TMath::Cos(scang);
107 // Beam divergence and crossing angle
108 if(fBeamDiv!=0.) {BeamDivCross(0,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
109 if(fBeamCrossAngle!=0.) {BeamDivCross(1,fBeamDiv,fBeamCrossAngle,fBeamCrossPlane,pLab);}
111 // If required apply the Fermi momentum
113 if((fIpart==kProton) || (fIpart==kNeutron)){
114 ExtractFermi(fIpart,fPp,fProbintp,fProbintn,ddp);
116 if(fIpart==kProton) {mass = 0.93956563;}
117 if(fIpart==kNeutron) {mass = 0.93827231;}
118 // printf(" pLABx = %f pLABy = %f pLABz = %f \n",pLab[0],pLab[1],pLab[2]);
122 balp0 = TMath::Sqrt(pLab[0]*pLab[0]+pLab[1]*pLab[1]+pLab[2]*pLab[2]+mass*mass);
126 dddp0 = TMath::Sqrt(dddp[0]*dddp[0]+dddp[1]*dddp[1]+dddp[2]*dddp[2]+mass*mass);
128 TVector3 b(balp[0]/balp0, balp[1]/balp0, balp[2]/balp0);
129 TLorentzVector pFermi(dddp[0], dddp[1], dddp[2], dddp0);
131 // printf(" pmu -> pLABx = %f pLABy = %f pLABz = %f E = %f\n",
132 // balp[0],balp[1],balp[2],balp0);
133 // printf(" Beta -> bx = %f by = %f bz = %f\n", b[0], b[1], b[2]);
134 // printf(" pFermi -> px = %f, py = %f, pz = %f\n", pFermi[0], pFermi[1], pFermi[2]);
138 // printf(" Boosted momentum -> px = %f, py = %f, pz = %f\n",
139 // pFermi[0], pFermi[1], pFermi[2]);
141 fBoostP[i] = pFermi[i];
146 Float_t polar[3] = {0,0,0};
147 gAlice->SetTrack(fTrackIt,-1,fIpart,fBoostP,fOrigin.GetArray(),polar,0,
151 //_____________________________________________________________________________
152 void AliGenZDC::FermiTwoGaussian(Double_t A, Float_t Z, Double_t* fPp, Double_t*
153 fProbintp, Double_t* fProbintn)
156 // Momenta distributions according to the "double-gaussian"
157 // distribution (Ilinov) - equal for protons and neutrons
159 // printf(" Initialization of Fermi momenta distribution\n");
162 Double_t sig1 = 0.113;
163 Double_t sig2 = 0.250;
164 Double_t alfa = 0.18*(TMath::Power((A/12.),(Float_t)1/3));
165 Double_t xk = (2*k2PI)/((1.+alfa)*(TMath::Power(k2PI,1.5)));
167 for(Int_t i=1; i<=200; i++){
168 Double_t p = i*0.005;
170 // printf(" fPp[%d] = %f\n",i,fPp[i]);
171 Double_t e1 = (p*p)/(2.*sig1*sig1);
172 Double_t e2 = (p*p)/(2.*sig2*sig2);
173 Double_t f1 = TMath::Exp(-(e1));
174 Double_t f2 = TMath::Exp(-(e2));
175 Double_t probp = xk*p*p*(f1/(TMath::Power(sig1,3.))+
176 alfa*f2/(TMath::Power(sig2,3.)))*0.005;
177 // printf(" probp = %f\n",probp);
178 fProbintp[i] = fProbintp[i-1] + probp;
179 fProbintn[i] = fProbintp[i];
180 // printf(" fProbintp[%d] = %f, fProbintp[%d] = %f\n",i,fProbintp[i],i,fProbintn[i]);
183 //_____________________________________________________________________________
184 void AliGenZDC::ExtractFermi(Int_t id, Double_t* fPp, Double_t* fProbintp,
185 Double_t* fProbintn, Double_t* ddp)
188 // Compute Fermi momentum for spectator nucleons
191 Float_t xx = gRandom->Rndm();
193 for(i=0; i<=200; i++){
194 if((xx>=fProbintp[i-1]) && (xx<fProbintp[i])) break;
197 else if(id==kNeutron){
198 for(i=0; i<=200; i++){
199 if((xx>=fProbintn[i-1]) && (xx<fProbintn[i])) break;
202 Float_t pext = fPp[i]+0.001;
203 Float_t phi = k2PI*(gRandom->Rndm());
204 Float_t cost = (1.-2.*(gRandom->Rndm()));
205 Float_t tet = TMath::ACos(cost);
206 ddp[0] = pext*TMath::Sin(tet)*TMath::Cos(phi);
207 ddp[1] = pext*TMath::Sin(tet)*TMath::Sin(phi);
211 //_____________________________________________________________________________
212 void AliGenZDC::BeamDivCross(Int_t icross, Float_t fBeamDiv, Float_t fBeamCrossAngle,
213 Int_t fBeamCrossPlane, Double_t* pLab)
215 Double_t tetpart, fipart, tetdiv, fidiv, angleSum[2], tetsum, fisum, dplab[3];
223 pmq = pmq+pLab[i]*pLab[i];
225 Double_t pmod = TMath::Sqrt(pmq);
226 // printf(" pmod = %f\n",pmod);
228 // printf(" icross = %d, fBeamDiv = %f\n",icross,fBeamDiv);
230 rvec = gRandom->Gaus(0.0,1.0);
231 tetdiv = fBeamDiv * TMath::Abs(rvec);
232 fidiv = (gRandom->Rndm())*k2PI;
235 if(fBeamCrossPlane==0.){
239 else if(fBeamCrossPlane==1.){
240 tetdiv = fBeamCrossAngle;
243 else if(fBeamCrossPlane==2.){
244 tetdiv = fBeamCrossAngle;
248 // printf(" tetdiv = %f, fidiv = %f\n",tetdiv,fidiv);
249 tetpart = TMath::ATan(TMath::Sqrt(dplab[0]*dplab[0]+dplab[1]*dplab[1])/dplab[2]);
250 if(dplab[1]!=0. || dplab[0]!=0.){
251 fipart = TMath::ATan2(dplab[1],dplab[0]);
256 if(fipart<0.) {fipart = fipart+k2PI;}
257 // printf(" tetpart = %f, fipart = %f\n",tetpart,fipart);
258 tetdiv = tetdiv*kRaddeg;
259 fidiv = fidiv*kRaddeg;
260 tetpart = tetpart*kRaddeg;
261 fipart = fipart*kRaddeg;
262 AddAngle(tetpart,fipart,tetdiv,fidiv,angleSum);
263 tetsum = angleSum[0];
265 // printf(" tetsum = %f, fisum = %f\n",tetsum,fisum);
266 tetsum = tetsum*kDegrad;
267 fisum = fisum*kDegrad;
268 pLab[0] = pmod*TMath::Sin(tetsum)*TMath::Cos(fisum);
269 pLab[1] = pmod*TMath::Sin(tetsum)*TMath::Sin(fisum);
270 pLab[2] = pmod*TMath::Cos(tetsum);
271 // printf(" pLab[0] = %f pLab[1] = %f pLab[2] = %f \n\n",
272 // pLab[0],pLab[1],pLab[2]);
278 //_____________________________________________________________________________
279 void AliGenZDC::AddAngle(Double_t theta1, Double_t phi1, Double_t theta2,
280 Double_t phi2, Double_t* angleSum)
282 Double_t temp, conv, cx, cy, cz, ct1, st1, ct2, st2, cp1, sp1, cp2, sp2;
283 Double_t rtetsum, tetsum, fisum;
286 conv = 180./TMath::ACos(temp);
288 ct1 = TMath::Cos(theta1/conv);
289 st1 = TMath::Sin(theta1/conv);
290 cp1 = TMath::Cos(phi1/conv);
291 sp1 = TMath::Sin(phi1/conv);
292 ct2 = TMath::Cos(theta2/conv);
293 st2 = TMath::Sin(theta2/conv);
294 cp2 = TMath::Cos(phi2/conv);
295 sp2 = TMath::Sin(phi2/conv);
296 cx = ct1*cp1*st2*cp2+st1*cp1*ct2-sp1*st2*sp2;
297 cy = ct1*sp1*st2*cp2+st1*sp1*ct2+cp1*st2*sp2;
298 cz = ct1*ct2-st1*st2*cp2;
300 rtetsum = TMath::ACos(cz);
301 tetsum = conv*rtetsum;
302 if(tetsum==0. || tetsum==180.){
306 temp = cx/TMath::Sin(rtetsum);
308 if(temp<-1.) temp=-1.;
309 fisum = conv*TMath::ACos(temp);
310 if(cy<0) {fisum = 360.-fisum;}
311 // printf(" AddAngle -> tetsum = %f, fisum = %f\n",tetsum, fisum);
312 angleSum[0] = tetsum;