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 // Parameterisation of pi and K, eta and pt distributions
19 // used for the ALICE TDRs.
20 // eta: according to HIJING (shadowing + quenching)
21 // pT : according to CDF measurement at 1.8 TeV
22 // Author: andreas.morsch@cern.ch
27 <img src="picts/AliGeneratorClass.gif">
30 <font size=+2 color=red>
31 <p>The responsible person for this module is
32 <a href="mailto:andreas.morsch@cern.ch">Andreas Morsch</a>.
38 ///////////////////////////////////////////////////////////////////
41 #include <TClonesArray.h>
42 #include <TDatabasePDG.h>
44 #include <TParticle.h>
48 #include "AliDecayer.h"
49 #include "AliGenEventHeader.h"
50 #include "AliGenHIJINGpara.h"
53 ClassImp(AliGenHIJINGpara)
56 AliGenHIJINGpara::AliGenHIJINGpara(const AliGenHIJINGpara & para):
63 //_____________________________________________________________________________
64 static Double_t ptpi(Double_t *px, Double_t *)
67 // PT-PARAMETERIZATION CDF, PRL 61(88) 1819
68 // POWER LAW FOR PT > 500 MEV
69 // MT SCALING BELOW (T=160 MEV)
71 const Double_t kp0 = 1.3;
72 const Double_t kxn = 8.28;
73 const Double_t kxlim=0.5;
74 const Double_t kt=0.160;
75 const Double_t kxmpi=0.139;
77 Double_t y, y1, xmpi2, ynorm, a;
80 y1=TMath::Power(kp0/(kp0+kxlim),kxn);
82 ynorm=kb*(TMath::Exp(-sqrt(kxlim*kxlim+xmpi2)/kt));
85 y=a*TMath::Power(kp0/(kp0+x),kxn);
87 y=kb*TMath::Exp(-sqrt(x*x+xmpi2)/kt);
91 //_____________________________________________________________________________
92 static Double_t ptscal(Double_t pt, Int_t np)
94 // SCALING EN MASSE PAR RAPPORT A PTPI
95 // MASS PI,K,ETA,RHO,OMEGA,ETA',PHI
96 const Double_t khm[10] = {.13957,.493,.5488,.769,.7826,.958,1.02,0,0,0};
97 // VALUE MESON/PI AT 5 GEV
98 const Double_t kfmax[10]={1.,0.3,0.55,1.0,1.0,1.0,1.0,0,0,0};
100 Double_t f5=TMath::Power(((
101 sqrt(100.018215)+2.)/(sqrt(100.+khm[np]*khm[np])+2.0)),12.3);
102 Double_t fmax2=f5/kfmax[np];
104 Double_t ptpion=100.*ptpi(&pt, (Double_t*) 0);
105 Double_t fmtscal=TMath::Power(((
106 sqrt(pt*pt+0.018215)+2.)/ (sqrt(pt*pt+khm[np]*khm[np])+2.0)),12.3)/
108 return fmtscal*ptpion;
111 //_____________________________________________________________________________
112 static Double_t ptka( Double_t *px, Double_t *)
115 // pt parametrisation for k
117 return ptscal(*px,2);
121 //_____________________________________________________________________________
122 static Double_t etapic( Double_t *py, Double_t *)
125 // eta parametrisation for pi
127 const Double_t ka1 = 4913.;
128 const Double_t ka2 = 1819.;
129 const Double_t keta1 = 0.22;
130 const Double_t keta2 = 3.66;
131 const Double_t kdeta1 = 1.47;
132 const Double_t kdeta2 = 1.51;
133 Double_t y=TMath::Abs(*py);
135 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
136 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
137 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
140 //_____________________________________________________________________________
141 static Double_t etakac( Double_t *py, Double_t *)
144 // eta parametrisation for ka
146 const Double_t ka1 = 497.6;
147 const Double_t ka2 = 215.6;
148 const Double_t keta1 = 0.79;
149 const Double_t keta2 = 4.09;
150 const Double_t kdeta1 = 1.54;
151 const Double_t kdeta2 = 1.40;
152 Double_t y=TMath::Abs(*py);
154 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
155 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
156 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
159 //_____________________________________________________________________________
160 AliGenHIJINGpara::AliGenHIJINGpara()
164 // Default constructor
177 //_____________________________________________________________________________
178 AliGenHIJINGpara::AliGenHIJINGpara(Int_t npart)
182 // Standard constructor
185 fTitle="HIJING Parametrisation Particle Generator";
197 //_____________________________________________________________________________
198 AliGenHIJINGpara::~AliGenHIJINGpara()
201 // Standard destructor
209 //_____________________________________________________________________________
210 void AliGenHIJINGpara::Init()
213 // Initialise the HIJING parametrisation
215 Float_t etaMin =-TMath::Log(TMath::Tan(
216 TMath::Min((Double_t)fThetaMax/2,TMath::Pi()/2-1.e-10)));
217 Float_t etaMax = -TMath::Log(TMath::Tan(
218 TMath::Max((Double_t)fThetaMin/2,1.e-10)));
219 fPtpi = new TF1("ptpi",&ptpi,0,20,0);
220 fPtka = new TF1("ptka",&ptka,0,20,0);
221 fETApic = new TF1("etapic",&etapic,etaMin,etaMax,0);
222 fETAkac = new TF1("etakac",&etakac,etaMin,etaMax,0);
224 TF1 etaPic0("etapic",&etapic,-7,7,0);
225 TF1 etaKac0("etakac",&etakac,-7,7,0);
227 TF1 ptPic0("ptpi",&ptpi,0.,15.,0);
228 TF1 ptKac0("ptka",&ptka,0.,15.,0);
230 Float_t intETApi = etaPic0.Integral(-0.5, 0.5);
231 Float_t intETAka = etaKac0.Integral(-0.5, 0.5);
232 Float_t scalePi = 7316/(intETApi/1.5);
233 Float_t scaleKa = 684/(intETAka/2.0);
235 // Fraction of events corresponding to the selected pt-range
236 Float_t intPt = (0.877*ptPic0.Integral(0, 15)+
237 0.123*ptKac0.Integral(0, 15));
238 Float_t intPtSel = (0.877*ptPic0.Integral(fPtMin, fPtMax)+
239 0.123*ptKac0.Integral(fPtMin, fPtMax));
240 Float_t ptFrac = intPtSel/intPt;
242 // Fraction of events corresponding to the selected eta-range
243 Float_t intETASel = (scalePi*etaPic0.Integral(etaMin, etaMax)+
244 scaleKa*etaKac0.Integral(etaMin, etaMax));
245 // Fraction of events corresponding to the selected phi-range
246 Float_t phiFrac = (fPhiMax-fPhiMin)/2/TMath::Pi();
248 fParentWeight = Float_t(fNpart)/(intETASel*ptFrac*phiFrac);
250 printf("%s: The number of particles in the selected kinematic region corresponds to %f percent of a full event\n ",
251 ClassName(),100.*fParentWeight);
253 // Issue warning message if etaMin or etaMax are outside the alowed range
254 // of the parametrization
255 if (etaMin < -8.001 || etaMax > 8.001) {
256 printf("\n \n WARNING FROM AliGenHIJINGPara !");
257 printf("\n YOU ARE USING THE PARAMETERISATION OUTSIDE ");
258 printf("\n THE ALLOWED PSEUDORAPIDITY RANGE (-8. - 8.)");
259 printf("\n YOUR LIMITS: %f %f \n \n ", etaMin, etaMax);
263 if (fPi0Decays && gMC)
264 fDecayer = gMC->GetDecayer();
268 //_____________________________________________________________________________
269 void AliGenHIJINGpara::Generate()
272 // Generate one trigger
276 const Float_t kRaKpic=0.14;
277 const Float_t kBorne=1/(1+kRaKpic);
278 Float_t polar[3]= {0,0,0};
280 const Int_t kPions[3] = {kPi0, kPiPlus, kPiMinus};
281 const Int_t kKaons[4] = {kK0Long, kK0Short, kKPlus, kKMinus};
284 Float_t pt, pl, ptot;
294 for (j=0;j<3;j++) origin[j]=fOrigin[j];
296 if(fVertexSmear == kPerEvent) {
298 for (j=0; j < 3; j++) origin[j] = fVertex[j];
302 eventVertex[0] = origin[0];
303 eventVertex[1] = origin[1];
304 eventVertex[2] = origin[2];
306 for(i=0;i<fNpart;i++) {
309 if(random[0]<kBorne) {
310 part=kPions[Int_t (random[1]*3)];
314 part=kKaons[Int_t (random[1]*4)];
318 phi=fPhiMin+random[2]*(fPhiMax-fPhiMin);
319 theta=2*TMath::ATan(TMath::Exp(-etaf->GetRandom()));
320 if(theta<fThetaMin || theta>fThetaMax) continue;
322 pl=pt/TMath::Tan(theta);
323 ptot=TMath::Sqrt(pt*pt+pl*pl);
324 if(ptot<fPMin || ptot>fPMax) continue;
325 p[0]=pt*TMath::Cos(phi);
326 p[1]=pt*TMath::Sin(phi);
328 if(fVertexSmear==kPerTrack) {
331 origin[j]=fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
332 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
335 if (part == kPi0 && fPi0Decays){
337 // Decay pi0 if requested
338 PushTrack(0,-1,part,p,origin,polar,0,kPPrimary,fNt,fParentWeight);
342 PushTrack(fTrackIt,-1,part,p,origin,polar,0,kPPrimary,fNt,fParentWeight);
348 SetHighWaterMark(fNt);
353 AliGenEventHeader* header = new AliGenEventHeader("HIJINGparam");
355 header->SetPrimaryVertex(eventVertex);
356 gAlice->SetGenEventHeader(header);
359 void AliGenHIJINGpara::SetPtRange(Float_t ptmin, Float_t ptmax) {
360 AliGenerator::SetPtRange(ptmin, ptmax);
363 void AliGenHIJINGpara::DecayPi0(Float_t* orig, Float_t * p)
367 // and put decay products on the stack
369 static TClonesArray *particles;
370 if(!particles) particles = new TClonesArray("TParticle",1000);
372 const Float_t kMass = TDatabasePDG::Instance()->GetParticle(kPi0)->Mass();
373 Float_t e = TMath::Sqrt(p[0] * p[0] + p[1] * p[1] + p[2] * p[2]+ kMass * kMass);
376 TLorentzVector pmom(p[0], p[1], p[2], e);
377 fDecayer->Decay(kPi0, &pmom);
380 // Put decay particles on the stack
382 Float_t polar[3] = {0., 0., 0.};
383 Int_t np = fDecayer->ImportParticles(particles);
385 for (Int_t i = 1; i < np; i++)
387 TParticle* iParticle = (TParticle *) particles->At(i);
388 p[0] = iParticle->Px();
389 p[1] = iParticle->Py();
390 p[2] = iParticle->Pz();
391 Int_t part = iParticle->GetPdgCode();
393 PushTrack(fTrackIt, fNt, part, p, orig, polar, 0, kPDecay, nt, fParentWeight);
399 void AliGenHIJINGpara::Copy(AliGenHIJINGpara &) const
401 Fatal("Copy","Not implemented!\n");