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 **************************************************************************/
19 // Generator using the TPythia interface (via AliPythia)
20 // to generate jets in pp collisions.
21 // Using SetNuclei() also nuclear modifications to the structure functions
22 // can be taken into account.
23 // Using SetQuenchingFactor(f) quenched jets can be modelled by superimposing
24 // two jets with energies e * f and e * (1-f)
26 // andreas.morsch@cern.ch
30 #include "AliGenPythiaJets.h"
32 #include <TParticle.h>
34 ClassImp(AliGenPythiaJets)
36 AliGenPythiaJets::AliGenPythiaJets()
39 // Default Constructor
42 AliGenPythiaJets::AliGenPythiaJets(Int_t npart)
46 fTitle= "Jet Generator using PYTHIA";
49 AliGenPythiaJets::AliGenPythiaJets(const AliGenPythiaJets & Pythia)
55 AliGenPythiaJets::~AliGenPythiaJets()
60 void AliGenPythiaJets::Init()
64 printf("AliGenPythiaJets::Init() \n");
69 fEtMinJetQ[0] = fEtMinJet * fQuench;
70 fEtMaxJetQ[0] = fEtMaxJet * fQuench;
71 fEtMinJetQ[1] = fEtMinJet * (1. - fQuench);
72 fEtMaxJetQ[1] = fEtMaxJet * (1. - fQuench);
73 fPtHardMinQ[0] = fPtHardMin * fQuench;
74 fPtHardMaxQ[0] = fPtHardMax * fQuench;
75 fPtHardMinQ[1] = fPtHardMin * (1. - fQuench);
76 fPtHardMaxQ[1] = fPtHardMax * (1. - fQuench);
80 void AliGenPythiaJets::Generate()
83 fDecayer->ForceDecay();
85 Float_t polar[3] = {0,0,0};
86 Float_t origin[3] = {0,0,0};
88 // converts from mm/c to s
89 const Float_t kconv=0.001/2.999792458e8;
97 // Set collision vertex position
98 if(fVertexSmear==kPerEvent) {
99 fPythia->SetMSTP(151,1);
101 fPythia->SetPARP(151+j, fOsigma[j]*10.);
103 } else if (fVertexSmear==kPerTrack) {
104 fPythia->SetMSTP(151,0);
110 fPythia->SetCKIN(3,fPtHardMinQ[jev]);
111 fPythia->SetCKIN(4,fPtHardMaxQ[jev]);
112 fEtMinJet = fEtMinJetQ[jev];
113 fEtMaxJet = fEtMaxJetQ[jev];
117 if (gAlice->GetEvNumber()>=fDebugEventFirst &&
118 gAlice->GetEvNumber()<=fDebugEventLast) fPythia->Pylist(1);
121 // Has this jet triggered
123 if ((fEtMinJet != -1) && ! CheckTrigger()) continue;
125 fPythia->ImportParticles(fParticles,"All");
127 Int_t np = fParticles->GetEntriesFast();
128 if (np == 0 ) continue;
129 // Get event vertex and discard the event if the z coord. is too big
130 TParticle *iparticle = (TParticle *) fParticles->At(0);
131 Float_t distz = iparticle->Vz()/10.;
132 if(TMath::Abs(distz)>fCutVertexZ*fOsigma[2]) continue;
135 fVertex[0] = iparticle->Vx()/10.+fOrigin.At(0);
136 fVertex[1] = iparticle->Vy()/10.+fOrigin.At(1);
137 fVertex[2] = iparticle->Vz()/10.+fOrigin.At(2);
139 Int_t* pParent = new Int_t[np];
140 for (i=0; i< np; i++) pParent[i] = -1;
144 for (i = 0; i<np; i++) {
146 TParticle * iparticle = (TParticle *) fParticles->At(i);
147 kf = CheckPDGCode(iparticle->GetPdgCode());
148 Int_t ks = iparticle->GetStatusCode();
149 Int_t km = iparticle->GetFirstMother();
150 if ((ks == 1 && kf !=0 && KinematicSelection(iparticle, 0)) ||
152 (fProcess == kPyJets && ks == 21 && km == 0 && i > 1)) {
154 if (ks == 1) trackIt = 1;
155 Int_t ipa = iparticle->GetFirstMother() - 1;
156 iparent = (ipa > -1) ? pParent[ipa] : -1;
158 // Store track information
160 p[0] = iparticle->Px();
161 p[1] = iparticle->Py();
162 p[2] = iparticle->Pz();
163 origin[0] = fOrigin[0]+iparticle->Vx()/10.;
164 origin[1] = fOrigin[1]+iparticle->Vy()/10.;
165 origin[2] = fOrigin[2]+iparticle->Vz()/10.;
166 Float_t tof=kconv*iparticle->T();
167 PushTrack(fTrackIt*trackIt, iparent, kf, p, origin, polar,
168 tof, kPPrimary, nt, 1., ks);
174 if (pParent) delete[] pParent;
175 printf("\n AliGenPythiaJets: I've put %i particles on the stack \n",nc);
178 if ((fQuench <= 0.) || (fQuench > 0. && jev == 2)) {
179 fKineBias=Float_t(fNpart)/Float_t(fTrials);
180 printf("\n Trials: %i %i %i\n",fTrials, fNpart, jev);
187 SetHighWaterMark(nt);
189 fXsection=fPythia->GetPARI(1);
192 Bool_t AliGenPythiaJets::CheckTrigger()
194 // Check the kinematic trigger condition
196 Bool_t triggered = kFALSE;
201 // Use Pythia clustering on parton level to determine jet axis
203 GetJets(njets, ntrig, jets);
207 Float_t px = jets[0][0];
208 Float_t py = jets[1][0];
209 Float_t pz = jets[2][0];
210 Float_t e = jets[3][0];
212 Float_t phi = TMath::Pi()+TMath::ATan2(-py,-px);
213 TransformEvent(beta, -2. * TMath::Pi() / 3. + phi);
218 AliGenPythiaJets& AliGenPythiaJets::operator=(const AliGenPythiaJets& rhs)
220 // Assignment operator
224 void AliGenPythiaJets::TransformEvent(Float_t beta, Float_t phi)
227 // Perform Lorentz Transformation and Rotation
229 Float_t gamma = 1./TMath::Sqrt(1. - beta * beta);
230 Int_t npart = (fPythia->GetPyjets())->N;
232 for (Int_t part = 0; part < npart; part++) {
233 Float_t px = (fPythia->GetPyjets())->P[0][part];
234 Float_t py = (fPythia->GetPyjets())->P[1][part];
235 Float_t pz = (fPythia->GetPyjets())->P[2][part];
236 Float_t e = (fPythia->GetPyjets())->P[3][part];
240 Float_t pzt = gamma * pz - gamma * beta * e;
241 Float_t et = -gamma * beta * pz + gamma * e;
245 Float_t pxt = TMath::Cos(phi) * px + TMath::Sin(phi) * py;
246 Float_t pyt = - TMath::Sin(phi) * px + TMath::Cos(phi) * py;
249 (fPythia->GetPyjets())->P[0][part] = pxt;
250 (fPythia->GetPyjets())->P[1][part] = pyt;
251 (fPythia->GetPyjets())->P[2][part] = pzt;
252 (fPythia->GetPyjets())->P[3][part] = et;