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. *
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8 * documentation strictly for non-commercial purposes is hereby granted *
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12 * about the suitability of this software for any purpose. It is *
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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>
45 #include <TParticle.h>
48 #include <TVirtualMC.h>
51 #include "AliDecayer.h"
52 #include "AliGenEventHeader.h"
53 #include "AliGenHIJINGpara.h"
56 ClassImp(AliGenHIJINGpara)
59 AliGenHIJINGpara::AliGenHIJINGpara(const AliGenHIJINGpara & para):
66 //_____________________________________________________________________________
67 static Double_t ptpi(Double_t *px, Double_t *)
70 // PT-PARAMETERIZATION CDF, PRL 61(88) 1819
71 // POWER LAW FOR PT > 500 MEV
72 // MT SCALING BELOW (T=160 MEV)
74 const Double_t kp0 = 1.3;
75 const Double_t kxn = 8.28;
76 const Double_t kxlim = 0.5;
77 const Double_t kt = 0.160;
78 const Double_t kxmpi = 0.139;
79 const Double_t kb = 1.;
80 Double_t y, y1, xmpi2, ynorm, a;
83 y1 = TMath::Power(kp0 / (kp0 + kxlim), kxn);
84 xmpi2 = kxmpi * kxmpi;
85 ynorm = kb * (TMath::Exp(-sqrt(kxlim * kxlim + xmpi2) / kt ));
88 y = a * TMath::Power(kp0 / (kp0 + x), kxn);
90 y = kb* TMath::Exp(-sqrt(x * x + xmpi2) / kt);
95 //_____________________________________________________________________________
96 static Double_t ptscal(Double_t pt, Int_t np)
98 // SCALING EN MASSE PAR RAPPORT A PTPI
99 // MASS PI,K,ETA,RHO,OMEGA,ETA',PHI
100 const Double_t khm[10] = {.13957,.493,.5488,.769,.7826,.958,1.02,0,0,0};
101 // VALUE MESON/PI AT 5 GEV
102 const Double_t kfmax[10]={1.,0.3,0.55,1.0,1.0,1.0,1.0,0,0,0};
104 Double_t f5=TMath::Power(((
105 sqrt(100.018215)+2.)/(sqrt(100.+khm[np]*khm[np])+2.0)),12.3);
106 Double_t fmax2=f5/kfmax[np];
108 Double_t ptpion=100.*ptpi(&pt, (Double_t*) 0);
109 Double_t fmtscal=TMath::Power(((
110 sqrt(pt*pt+0.018215)+2.)/ (sqrt(pt*pt+khm[np]*khm[np])+2.0)),12.3)/
112 return fmtscal*ptpion;
115 //_____________________________________________________________________________
116 static Double_t ptka( Double_t *px, Double_t *)
119 // pt parametrisation for k
121 return ptscal(*px,2);
125 //_____________________________________________________________________________
126 static Double_t etapic( Double_t *py, Double_t *)
129 // eta parametrisation for pi
131 const Double_t ka1 = 4913.;
132 const Double_t ka2 = 1819.;
133 const Double_t keta1 = 0.22;
134 const Double_t keta2 = 3.66;
135 const Double_t kdeta1 = 1.47;
136 const Double_t kdeta2 = 1.51;
137 Double_t y=TMath::Abs(*py);
139 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
140 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
141 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
144 //_____________________________________________________________________________
145 static Double_t etakac( Double_t *py, Double_t *)
148 // eta parametrisation for ka
150 const Double_t ka1 = 497.6;
151 const Double_t ka2 = 215.6;
152 const Double_t keta1 = 0.79;
153 const Double_t keta2 = 4.09;
154 const Double_t kdeta1 = 1.54;
155 const Double_t kdeta2 = 1.40;
156 Double_t y=TMath::Abs(*py);
158 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
159 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
160 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
163 //_____________________________________________________________________________
164 AliGenHIJINGpara::AliGenHIJINGpara()
168 // Default constructor
181 //_____________________________________________________________________________
182 AliGenHIJINGpara::AliGenHIJINGpara(Int_t npart)
186 // Standard constructor
189 fTitle="HIJING Parametrisation Particle Generator";
201 //_____________________________________________________________________________
202 AliGenHIJINGpara::~AliGenHIJINGpara()
205 // Standard destructor
213 //_____________________________________________________________________________
214 void AliGenHIJINGpara::Init()
217 // Initialise the HIJING parametrisation
219 Float_t etaMin =-TMath::Log(TMath::Tan(
220 TMath::Min((Double_t)fThetaMax/2,TMath::Pi()/2-1.e-10)));
221 Float_t etaMax = -TMath::Log(TMath::Tan(
222 TMath::Max((Double_t)fThetaMin/2,1.e-10)));
223 fPtpi = new TF1("ptpi",&ptpi,0,20,0);
224 fPtka = new TF1("ptka",&ptka,0,20,0);
227 fETApic = new TF1("etapic",&etapic,etaMin,etaMax,0);
228 fETAkac = new TF1("etakac",&etakac,etaMin,etaMax,0);
230 TF1 etaPic0("etaPic0",&etapic,-7,7,0);
231 TF1 etaKac0("etaKac0",&etakac,-7,7,0);
233 TF1 ptPic0("ptPic0",&ptpi,0.,15.,0);
234 TF1 ptKac0("ptKac0",&ptka,0.,15.,0);
236 Float_t intETApi = etaPic0.Integral(-0.5, 0.5);
237 Float_t intETAka = etaKac0.Integral(-0.5, 0.5);
238 Float_t scalePi = 7316/(intETApi/1.5);
239 Float_t scaleKa = 684/(intETAka/2.0);
241 // Fraction of events corresponding to the selected pt-range
242 Float_t intPt = (0.877*ptPic0.Integral(0, 15)+
243 0.123*ptKac0.Integral(0, 15));
244 Float_t intPtSel = (0.877*ptPic0.Integral(fPtMin, fPtMax)+
245 0.123*ptKac0.Integral(fPtMin, fPtMax));
246 Float_t ptFrac = intPtSel/intPt;
248 // Fraction of events corresponding to the selected eta-range
249 Float_t intETASel = (scalePi*etaPic0.Integral(etaMin, etaMax)+
250 scaleKa*etaKac0.Integral(etaMin, etaMax));
251 // Fraction of events corresponding to the selected phi-range
252 Float_t phiFrac = (fPhiMax-fPhiMin)/2/TMath::Pi();
255 fParentWeight = Float_t(fNpart)/(intETASel*ptFrac*phiFrac);
258 fPtWgtPi = (fPtMax - fPtMin) / fPtpi->Integral(0., 20.);
259 fPtWgtKa = (fPtMax - fPtMin) / fPtka->Integral(0., 20.);
260 fParentWeight = Float_t(fNpart)/(intETASel*phiFrac);
264 printf("%s: The number of particles in the selected kinematic region corresponds to %f percent of a full event\n ",
265 ClassName(),100.*fParentWeight);
267 // Issue warning message if etaMin or etaMax are outside the alowed range
268 // of the parametrization
269 if (etaMin < -8.001 || etaMax > 8.001) {
270 printf("\n \n WARNING FROM AliGenHIJINGPara !");
271 printf("\n YOU ARE USING THE PARAMETERISATION OUTSIDE ");
272 printf("\n THE ALLOWED PSEUDORAPIDITY RANGE (-8. - 8.)");
273 printf("\n YOUR LIMITS: %f %f \n \n ", etaMin, etaMax);
277 if (fPi0Decays && gMC)
278 fDecayer = gMC->GetDecayer();
282 //_____________________________________________________________________________
283 void AliGenHIJINGpara::Generate()
286 // Generate one trigger
290 const Float_t kRaKpic=0.14;
291 const Float_t kBorne=1/(1+kRaKpic);
292 Float_t polar[3]= {0,0,0};
294 const Int_t kPions[3] = {kPi0, kPiPlus, kPiMinus};
295 const Int_t kKaons[4] = {kK0Long, kK0Short, kKPlus, kKMinus};
298 Float_t pt, pl, ptot, wgt;
308 for (j=0;j<3;j++) origin[j]=fOrigin[j];
310 if(fVertexSmear == kPerEvent) {
312 for (j=0; j < 3; j++) origin[j] = fVertex[j];
316 eventVertex[0] = origin[0];
317 eventVertex[1] = origin[1];
318 eventVertex[2] = origin[2];
320 for(i=0;i<fNpart;i++) {
323 if(random[0]<kBorne) {
324 part=kPions[Int_t (random[1]*3)];
329 part=kKaons[Int_t (random[1]*4)];
334 phi=fPhiMin+random[2]*(fPhiMax-fPhiMin);
335 theta=2*TMath::ATan(TMath::Exp(-etaf->GetRandom()));
336 if(theta<fThetaMin || theta>fThetaMax) continue;
339 pt = ptf->GetRandom();
341 pt = fPtMin + random[3] * (fPtMax - fPtMin);
345 pl=pt/TMath::Tan(theta);
346 ptot=TMath::Sqrt(pt*pt+pl*pl);
347 if(ptot<fPMin || ptot>fPMax) continue;
348 p[0]=pt*TMath::Cos(phi);
349 p[1]=pt*TMath::Sin(phi);
351 if(fVertexSmear==kPerTrack) {
354 origin[j]=fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
355 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
362 wgt *= (fParentWeight * ptf->Eval(pt));
366 if (part == kPi0 && fPi0Decays){
368 // Decay pi0 if requested
369 PushTrack(0,-1,part,p,origin,polar,0,kPPrimary,fNt,fParentWeight);
373 PushTrack(fTrackIt,-1,part,p,origin,polar,0,kPPrimary,fNt,fParentWeight);
379 SetHighWaterMark(fNt);
384 AliGenEventHeader* header = new AliGenEventHeader("HIJINGparam");
386 header->SetPrimaryVertex(eventVertex);
387 gAlice->SetGenEventHeader(header);
390 void AliGenHIJINGpara::SetPtRange(Float_t ptmin, Float_t ptmax) {
391 AliGenerator::SetPtRange(ptmin, ptmax);
394 void AliGenHIJINGpara::DecayPi0(Float_t* orig, Float_t * p)
398 // and put decay products on the stack
400 static TClonesArray *particles;
401 if(!particles) particles = new TClonesArray("TParticle",1000);
403 const Float_t kMass = TDatabasePDG::Instance()->GetParticle(kPi0)->Mass();
404 Float_t e = TMath::Sqrt(p[0] * p[0] + p[1] * p[1] + p[2] * p[2]+ kMass * kMass);
407 TLorentzVector pmom(p[0], p[1], p[2], e);
408 fDecayer->Decay(kPi0, &pmom);
411 // Put decay particles on the stack
413 Float_t polar[3] = {0., 0., 0.};
414 Int_t np = fDecayer->ImportParticles(particles);
416 for (Int_t i = 1; i < np; i++)
418 TParticle* iParticle = (TParticle *) particles->At(i);
419 p[0] = iParticle->Px();
420 p[1] = iParticle->Py();
421 p[2] = iParticle->Pz();
422 Int_t part = iParticle->GetPdgCode();
424 PushTrack(fTrackIt, fNt, part, p, orig, polar, 0, kPDecay, nt, fParentWeight);
430 void AliGenHIJINGpara::Copy(TObject &) const
432 Fatal("Copy","Not implemented!\n");
436 void AliGenHIJINGpara::Draw( const char * /*opt*/)
439 // Draw the pT and y Distributions
441 TCanvas *c0 = new TCanvas("c0","Canvas 0",400,10,600,700);
445 fPtpi->GetHistogram()->SetXTitle("p_{T} (GeV)");
448 fPtka->GetHistogram()->SetXTitle("p_{T} (GeV)");