--- /dev/null
+/**************************************************************************
+ * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
+ * *
+ * Author: The ALICE Off-line Project. *
+ * Contributors are mentioned in the code where appropriate. *
+ * *
+ * Permission to use, copy, modify and distribute this software and its *
+ * documentation strictly for non-commercial purposes is hereby granted *
+ * without fee, provided that the above copyright notice appears in all *
+ * copies and that both the copyright notice and this permission notice *
+ * appear in the supporting documentation. The authors make no claims *
+ * about the suitability of this software for any purpose. It is *
+ * provided "as is" without express or implied warranty. *
+ **************************************************************************/
+
+/* $Id$ */
+
+// Class to generate correlated Heavy Flavor hadron pairs (one or several pairs
+// per event) using paramtrized kinematics of quark pairs from some generator
+// and quark fragmentation functions.
+// Is a generalisation of AliGenParam class for correlated pairs of hadrons.
+// In this version quark pairs and fragmentation functions are obtained from
+// Pythia6.124 using 100K events generated with kCharmppMNRwmi & kBeautyppMNRwmi
+// in pp collisions at 14 TeV.
+// Decays are performed by Pythia. Used AliRoot version: v4-04-Release
+// Author: S. Grigoryan, LPC Clermont-Fd & YerPhI, Smbat.Grigoryan@cern.ch
+//
+//-------------------------------------------------------------------------
+// How it works (for the given flavor):
+//
+// 1) Reads QQbar kinematical grid from the Input file and generates
+// quark pairs according to the weights of the cells.
+// It is a 5D grid in y1,y2,pt1,pt2 and deltaphi, with occupancy weights
+// of the cells obtained from Pythia (see details in GetQuarkPair).
+// 2) Reads "soft" and "hard" fragmentation functions (12 2D-histograms each,
+// for 12 pt bins) from the Input file, applies to quarks and produces hadrons
+// (only lower states, with proportions of species obtained from Pythia).
+// Fragmentation functions are the same for all hadron species and depend
+// on 2 variables - light cone energy-momentum fractions:
+// z1=(E_H + Pz_H)/(E_Q + Pz_Q), z2=(E_H - Pz_H)/(E_Q - Pz_Q).
+// "soft" & "hard" FFs correspond to "slower" & "faster" quark of a pair
+// (see details in GetHadronPair).
+// 3) Decays the hadrons and saves all the particles in the event stack in the
+// following order: HF hadron from Q, then its decay products, then HF hadron
+// from Qbar, then its decay productes, then next HF hadon pair (if any)
+// in the same way, etc...
+// 4) It is fast, e.g., generates the same number of events with a beauty pair
+// ~15 times faster than AliGenPythia with kBeautyppMNRwmi (w/o tracking)
+//
+// An Input file for each quark flavor is included in EVGEN/dataCorrHF/
+// One can use also user-defined Input files.
+//
+// More details could be found in my presentation at DiMuonNet Workshop, Dec 2006:
+// http://www-dapnia.cea.fr/Sphn/Alice/DiMuonNet
+// and will be published in an Internal Note.
+//
+//-------------------------------------------------------------------------
+// How to use it:
+//
+// add the following typical lines in Config.C
+/*
+ if (!strcmp(option,"corr")) {
+ // Example for correlated charm or beauty hadron pair production
+
+ // AliGenCorrHF *gener = new AliGenCorrHF(1, 4); // for charm, 1 pair per event
+ AliGenCorrHF *gener = new AliGenCorrHF(1, 5); // for beauty, 1 pair per event
+
+ gener->SetMomentumRange(0,9999);
+ gener->SetCutOnChild(0); // 1/0 means cuts on children enable/disable
+ gener->SetChildThetaRange(171.0,178.0);
+ gener->SetOrigin(0,0,0); //vertex position
+ gener->SetSigma(0,0,0); //Sigma in (X,Y,Z) (cm) on IP position
+ gener->SetForceDecay(kSemiMuonic);
+ gener->SetTrackingFlag(0);
+ gener->Init();
+}
+*/
+// and in aliroot do e.g. gAlice->Run(10,"Config.C") to produce 10 events.
+// One can include AliGenCorrHF in an AliGenCocktail generator.
+//--------------------------------------------------------------------------
+
+#include <TFile.h>
+#include <TTree.h>
+#include <TH2F.h>
+#include <TMath.h>
+#include <TRandom.h>
+#include <TROOT.h>
+#include <TLorentzVector.h>
+#include <TParticle.h>
+#include <TParticlePDG.h>
+#include <TDatabasePDG.h>
+#include <TVirtualMC.h>
+#include <TCanvas.h>
+#include <Riostream.h>
+
+#include "AliGenCorrHF.h"
+#include "AliLog.h"
+#include "AliConst.h"
+#include "AliDecayer.h"
+#include "AliMC.h"
+#include "AliRun.h"
+
+ClassImp(AliGenCorrHF)
+
+ //Begin_Html
+ /*
+ <img src="picts/AliGenCorrHF.gif">
+ */
+ //End_Html
+
+Double_t AliGenCorrHF::fgdph[19] = {0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180};
+Double_t AliGenCorrHF::fgy[31] = {-10,-7, -6.5, -6, -5.5, -5, -4.5, -4, -3.5, -3, -2.5, -2,- 1.5, -1, -0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 10};
+Double_t AliGenCorrHF::fgpt[33] = {0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.6, 7.2, 7.8, 8.4, 9, 9.6, 10.3, 11.1, 12, 13.1, 14.3, 15.6, 17.1, 19, 21, 24, 28, 35, 50, 100};
+Int_t AliGenCorrHF::fgnptbins = 12;
+Double_t AliGenCorrHF::fgptbmin[12] = {0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 9};
+Double_t AliGenCorrHF::fgptbmax[12] = {0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 9, 100};
+
+Double_t* AliGenCorrHF::fgIntegral = 0;
+
+//____________________________________________________________
+ AliGenCorrHF::AliGenCorrHF():
+ fFileName(0),
+ fFile(0),
+ fQuark(0),
+ fBias(0.),
+ fTrials(0),
+ fDecayer(0)
+{
+// Default constructor
+}
+
+//____________________________________________________________
+AliGenCorrHF::AliGenCorrHF(Int_t npart, Int_t param):
+ AliGenMC(npart),
+ fFileName(0),
+ fFile(0),
+ fQuark(param),
+ fBias(0.),
+ fTrials(0),
+ // fDecayer(new AliDecayerPythia())
+ fDecayer(0)
+{
+// Constructor using number of particles, quark type & default InputFile
+//
+ if (fQuark != 5) fQuark = 4;
+ fFileName = "$ALICE_ROOT/EVGEN/dataCorrHF/CharmppMNRwmiCorr100K.root";
+ if (fQuark == 5) fFileName = "$ALICE_ROOT/EVGEN/dataCorrHF/BeautyppMNRwmiCorr100K.root";
+
+ fName = "Default";
+ fTitle= "Generator for correlated pairs of HF hadrons";
+
+ fChildSelect.Set(5);
+ for (Int_t i=0; i<5; i++) fChildSelect[i]=0;
+ SetForceDecay();
+ SetCutOnChild();
+ SetChildMomentumRange();
+ SetChildPtRange();
+ SetChildPhiRange();
+ SetChildThetaRange();
+}
+
+//___________________________________________________________________
+AliGenCorrHF::AliGenCorrHF(char* tname, Int_t npart, Int_t param):
+ AliGenMC(npart),
+ fFileName(tname),
+ fFile(0),
+ fQuark(param),
+ fBias(0.),
+ fTrials(0),
+ // fDecayer(new AliDecayerPythia())
+ fDecayer(0)
+{
+// Constructor using number of particles, quark type & user-defined InputFile
+//
+ if (fQuark != 5) fQuark = 4;
+ fName = "UserDefined";
+ fTitle= "Generator for correlated pairs of HF hadrons";
+
+ fChildSelect.Set(5);
+ for (Int_t i=0; i<5; i++) fChildSelect[i]=0;
+ SetForceDecay();
+ SetCutOnChild();
+ SetChildMomentumRange();
+ SetChildPtRange();
+ SetChildPhiRange();
+ SetChildThetaRange();
+}
+
+//____________________________________________________________
+AliGenCorrHF::AliGenCorrHF(const AliGenCorrHF & CorrHF)
+ :AliGenMC(CorrHF),
+ fFileName(0),
+ fFile(0),
+ fQuark(0),
+ fBias(0.),
+ fTrials(0),
+ fDecayer(0)
+{
+// Copy constructor
+ CorrHF.Copy(*this);
+}
+
+//____________________________________________________________
+AliGenCorrHF::~AliGenCorrHF()
+{
+// Destructor
+ delete fFile;
+}
+
+//____________________________________________________________
+void AliGenCorrHF::Init()
+{
+// Initialisation
+
+ AliInfo(Form(" QQbar kinematics and fragm. functions from: %s",fFileName.Data() ));
+ fFile = TFile::Open(fFileName.Data());
+ if(!fFile->IsOpen()){
+ AliError(Form("Could not open file %s",fFileName.Data() ));
+ }
+
+ ComputeIntegral(fFile);
+
+ fParentWeight = 1./fNpart; // fNpart is number of HF-hadron pairs
+
+// particle decay related initialization
+
+ if (gMC) fDecayer = gMC->GetDecayer();
+ fDecayer->SetForceDecay(fForceDecay);
+ fDecayer->Init();
+
+//
+ AliGenMC::Init();
+}
+
+//____________________________________________________________
+void AliGenCorrHF::Generate()
+{
+//
+// Generate fNpart of correlated HF hadron pairs per event
+// in the the desired theta and momentum windows (phi = 0 - 2pi).
+// Gaussian smearing on the vertex is done if selected.
+// The decay of heavy hadrons is done using lujet,
+// and the childern particle are tracked by GEANT
+// However, light mesons are directly tracked by GEANT
+// setting fForceDecay = nodecay (SetForceDecay(nodecay))
+//
+
+
+ Float_t polar[3]= {0,0,0}; // Polarisation of the parent particle (for GEANT tracking)
+ Float_t origin0[3]; // Origin of the generated parent particle (for GEANT tracking)
+ Float_t pt, pl, ptot; // Transverse, logitudinal and total momenta of the parent particle
+ Float_t phi, theta; // Phi and theta spherical angles of the parent particle momentum
+ Float_t p[3], pc[3], och[3];// Momentum, polarisation and origin of the children particles from lujet
+
+
+ Double_t dphi=0, ptq[2], yq[2], pth[2], plh[2], ph[2], phih[2];
+ Int_t i, j, ipair, ihadron[2];
+ for (i=0; i<2; i++) {
+ ptq[i] =0;
+ yq[i] =0;
+ pth[i] =0;
+ plh[i] =0;
+ ihadron[i] =0;
+ }
+
+ static TClonesArray *particles;
+ //
+ if(!particles) particles = new TClonesArray("TParticle",1000);
+
+ TDatabasePDG* pDataBase = TDatabasePDG::Instance();
+
+// Calculating vertex position per event
+ for (j=0;j<3;j++) origin0[j]=fOrigin[j];
+ if(fVertexSmear==kPerEvent) {
+ Vertex();
+ for (j=0;j<3;j++) origin0[j]=fVertex[j];
+ }
+
+ Float_t wgtp, wgtch, random[6];
+ Int_t ipap = 0;
+ Int_t nt = 0;
+
+// Generating fNpart HF-hadron pairs per event
+ while(ipap<fNpart) {
+
+ while(1) {
+
+ GetQuarkPair(fFile, fgIntegral, yq[0], yq[1], ptq[0], ptq[1], dphi);
+
+ GetHadronPair(fFile, fQuark, yq[0], yq[1], ptq[0], ptq[1], ihadron[0], ihadron[1], plh[0], plh[1], pth[0], pth[1]);
+
+// Here we assume that |phi_H1 - phi_H2| = |phi_Q1 - phi_Q2| = dphi
+// which is a good approximation for heavy flavors in Pythia
+
+ /* // doesn't work if PhiMax < k2PI or PhiMin > 0, since dphi = 0 - 180
+ phih[0] = fPhiMin + Rndm()*(fPhiMax-fPhiMin);
+ phih[1] = phih[0] + dphi*kDegrad;
+ if (phih[0] > fPhiMax/2.) phih[1] = phih[0] - dphi*kDegrad;
+ */
+ phih[0] = Rndm()*k2PI;
+ phih[1] = phih[0] + dphi*kDegrad;
+ if (phih[0] > TMath::Pi()) phih[1] = phih[0] - dphi*kDegrad;
+
+// Cut on theta
+ theta=TMath::ATan2(pth[0],plh[0]);
+ if(theta<fThetaMin || theta>fThetaMax) continue;
+ theta=TMath::ATan2(pth[1],plh[1]);
+ if(theta<fThetaMin || theta>fThetaMax) continue;
+
+// Cut on momentum
+ ph[0]=TMath::Sqrt(pth[0]*pth[0]+plh[0]*plh[0]);
+ if (ph[0]<fPMin || ph[0]>fPMax) continue;
+ ph[1]=TMath::Sqrt(pth[1]*pth[1]+plh[1]*plh[1]);
+ if (ph[1]<fPMin || ph[1]>fPMax) continue;
+
+// Common origin for particles of the HF-hadron pair
+ if(fVertexSmear==kPerTrack) {
+ Rndm(random,6);
+ for (j=0;j<3;j++) {
+ origin0[j]=
+ fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
+ TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
+ }
+ }
+
+ Int_t np1=0, kf1[100], select1[100], iparent1[100], trackIt1[100];
+ Float_t wgtch1=0, p1[3], pc1[100][3], och1[100][3];
+
+ for (j=0; j<3; j++) p1[j] = 0;
+ for (i=0; i<100; i++) {
+ kf1[i] = 0;
+ select1[i] = 0;
+ iparent1[i] = 0;
+ trackIt1[i] = 0;
+ for (j=0; j<3; j++) {
+ pc1[i][j] = 0;
+ och1[i][j] = 0;
+ }
+ }
+
+//
+// Loop over particles of the HF-hadron pair
+ Int_t nhadron = 0;
+ for (ipair=0;ipair<2;ipair++) {
+ phi = phih[ipair];
+ pl = plh[ipair];
+ pt = pth[ipair];
+ ptot = ph[ipair];
+//
+// particle type
+ Int_t iPart = ihadron[ipair];
+ Float_t am = pDataBase->GetParticle(iPart)->Mass();
+ fChildWeight=(fDecayer->GetPartialBranchingRatio(iPart))*fParentWeight;
+
+ wgtp = fParentWeight;
+ wgtch = fChildWeight;
+
+//
+ p[0]=pt*TMath::Cos(phi);
+ p[1]=pt*TMath::Sin(phi);
+ p[2]=pl;
+
+// Looking at fForceDecay :
+// if fForceDecay != none Primary particle decays using
+// AliPythia and children are tracked by GEANT
+//
+// if fForceDecay == none Primary particle is tracked by GEANT
+// (In the latest, make sure that GEANT actually does all the decays you want)
+//
+
+ if (fForceDecay != kNoDecay) {
+// Using lujet to decay particle
+ Float_t energy=TMath::Sqrt(ptot*ptot+am*am);
+ TLorentzVector pmom(p[0], p[1], p[2], energy);
+ fDecayer->Decay(iPart,&pmom);
+//
+// select decay particles
+ Int_t np=fDecayer->ImportParticles(particles);
+
+// Selecting GeometryAcceptance for particles fPdgCodeParticleforAcceptanceCut;
+ if (fGeometryAcceptance)
+ if (!CheckAcceptanceGeometry(np,particles)) break;
+ Int_t ncsel=0;
+ Int_t* pParent = new Int_t[np];
+ Int_t* pSelected = new Int_t[np];
+ Int_t* trackIt = new Int_t[np];
+
+ for (i=0; i<np; i++) {
+ pSelected[i] = 0;
+ pParent[i] = -1;
+ }
+
+ if (np >1) {
+ TParticle* iparticle = (TParticle *) particles->At(0);
+ for (i=1; i<np; i++) {
+ trackIt[i] = 1;
+ iparticle = (TParticle *) particles->At(i);
+ Int_t kf = iparticle->GetPdgCode();
+ Int_t ks = iparticle->GetStatusCode();
+
+// particles with long life-time (c tau > .3 mum)
+ if (ks != 1) {
+ Double_t lifeTime = fDecayer->GetLifetime(kf);
+ if (lifeTime <= (Double_t) fMaxLifeTime) {
+ trackIt[i] = 0;
+ pSelected[i] = 1;
+ }
+ } // ks==1 ?
+//
+// children, discard neutrinos
+ if (TMath::Abs(kf) == 12 || TMath::Abs(kf) == 14) continue;
+ if (trackIt[i])
+ {
+ if (fCutOnChild) {
+ pc[0]=iparticle->Px();
+ pc[1]=iparticle->Py();
+ pc[2]=iparticle->Pz();
+ Bool_t childok = KinematicSelection(iparticle, 1);
+ if(childok) {
+ pSelected[i] = 1;
+ ncsel++;
+ } else {
+ ncsel=-1;
+ break;
+ } // child kine cuts
+ } else {
+ pSelected[i] = 1;
+ ncsel++;
+ } // if child selection
+ } // select muon
+ } // decay particle loop
+ } // if decay products
+
+ Int_t iparent;
+ if ((fCutOnChild && ncsel >0) || !fCutOnChild){
+
+ nhadron++;
+//
+// Parents and Decay Products
+ if (ipair == 0) {
+ np1 = np;
+ wgtch1 = wgtch;
+ p1[0] = p[0]; p1[1] = p[1]; p1[2] = p[2];
+ } else {
+ ipap++;
+ PushTrack(0, -1, ihadron[0], p1, origin0, polar, 0,
+ kPPrimary, nt, wgtp);
+ KeepTrack(nt);
+ for (i = 1; i < np1; i++) {
+ if (select1[i]) {
+ for (j=0; j<3; j++) {
+ och[j] = och1[i][j];
+ pc[j] = pc1[i][j];
+ }
+ PushTrack(fTrackIt*trackIt1[i], iparent1[i], kf1[i], pc, och,
+ polar, 0, kPDecay, nt, wgtch1);
+ KeepTrack(nt);
+ }
+ }
+ PushTrack(0, -1, iPart, p, origin0, polar, 0, kPPrimary, nt, wgtp);
+ KeepTrack(nt);
+ }
+ pParent[0] = nt;
+//
+// Decay Products
+ Int_t ntcount = 0;
+ for (i = 1; i < np; i++) {
+ if (pSelected[i]) {
+ TParticle* iparticle = (TParticle *) particles->At(i);
+ Int_t kf = iparticle->GetPdgCode();
+ Int_t ipa = iparticle->GetFirstMother()-1;
+
+ och[0] = origin0[0]+iparticle->Vx()/10;
+ och[1] = origin0[1]+iparticle->Vy()/10;
+ och[2] = origin0[2]+iparticle->Vz()/10;
+ pc[0] = iparticle->Px();
+ pc[1] = iparticle->Py();
+ pc[2] = iparticle->Pz();
+
+ if (ipa > -1) {
+ iparent = pParent[ipa];
+ } else {
+ iparent = -1;
+ }
+
+ if (ipair == 0) {
+ kf1[i] = kf;
+ select1[i] = pSelected[i];
+ iparent1[i] = iparent;
+ trackIt1[i] = trackIt[i];
+ for (j=0; j<3; j++) {
+ och1[i][j] = och[j];
+ pc1[i][j] = pc[j];
+ }
+ ntcount++;
+ } else {
+ PushTrack(fTrackIt*trackIt[i], iparent, kf, pc, och,
+ polar, 0, kPDecay, nt, wgtch);
+ KeepTrack(nt);
+ }
+ pParent[i] = nt + ntcount;
+ } // Selected
+ } // Particle loop
+ } // Decays by Lujet
+ particles->Clear();
+ if (pParent) delete[] pParent;
+ if (pSelected) delete[] pSelected;
+ if (trackIt) delete[] trackIt;
+ } // kinematic selection
+ else // nodecay option, so parent will be tracked by GEANT
+ {
+ nhadron++;
+ if (ipair == 0) {
+ p1[0] = p[0]; p1[1] = p[1]; p1[2] = p[2];
+ } else {
+ ipap++;
+ gAlice->GetMCApp()->
+ PushTrack(fTrackIt,-1,ihadron[0],p1,origin0,polar,0,kPPrimary,nt,wgtp);
+ gAlice->GetMCApp()->
+ PushTrack(fTrackIt,-1,iPart,p,origin0,polar,0,kPPrimary,nt,wgtp);
+ }
+ }
+ if (nhadron == 0) break;
+ } // ipair loop
+ if (nhadron != 2) continue;
+ break;
+ } // while(1)
+ nt++;
+ } // while(ipa<fNpart) --> event loop
+
+ SetHighWaterMark(nt);
+}
+
+//____________________________________________________________________________________
+AliGenCorrHF& AliGenCorrHF::operator=(const AliGenCorrHF& rhs)
+{
+// Assignment operator
+ rhs.Copy(*this);
+ return *this;
+}
+
+//____________________________________________________________________________________
+Int_t AliGenCorrHF::IpCharm(TRandom* ran)
+{
+// Composition of lower state charm hadrons, containing a c-quark
+ Float_t random;
+ Int_t ip; // +- 411,421,431,4122,4132,4232,4332
+ random = ran->Rndm();
+// Rates from Pythia6.214 using 100Kevents with kPyCharmppMNRwmi at 14 TeV.
+
+ if (random < 0.6027) {
+ ip=421;
+ } else if (random < 0.7962) {
+ ip=411;
+ } else if (random < 0.9127) {
+ ip=431;
+ } else if (random < 0.9899) {
+ ip=4122;
+ } else if (random < 0.9948) {
+ ip=4132;
+ } else if (random < 0.9999) {
+ ip=4232;
+ } else {
+ ip=4332;
+ }
+
+ return ip;
+}
+
+Int_t AliGenCorrHF::IpBeauty(TRandom* ran)
+{
+// Composition of lower state beauty hadrons, containing a b-quark
+ Float_t random;
+ Int_t ip; // +- 511,521,531,5122,5132,5232,5332
+ random = ran->Rndm();
+// Rates from Pythia6.214 using 100Kevents with kPyBeautyppMNRwmi at 14 TeV.
+ // B-Bbar mixing will be done by Pythia at the decay point
+ if (random < 0.3965) {
+ ip=-511;
+ } else if (random < 0.7930) {
+ ip=-521;
+ } else if (random < 0.9112) {
+ ip=-531;
+ } else if (random < 0.9887) {
+ ip=5122;
+ } else if (random < 0.9943) {
+ ip=5132;
+ } else if (random < 0.9999) {
+ ip=5232;
+ } else {
+ ip=5332;
+ }
+
+ return ip;
+}
+
+//____________________________________________________________________________________
+Double_t AliGenCorrHF::ComputeIntegral(TFile* fG) // needed by GetQuarkPair
+{
+ // Read QQbar kinematical 5D grid's cell occupancy weights
+ Int_t* cell = new Int_t[6]; // cell[6]={wght,iy1,iy2,ipt1,ipt2,idph}
+ TTree* tG = (TTree*) fG->Get("tGqq");
+ tG->GetBranch("cell")->SetAddress(cell);
+ Int_t nbins = tG->GetEntries();
+
+ // delete previously computed integral (if any)
+ if(fgIntegral) delete [] fgIntegral;
+
+ fgIntegral = new Double_t[nbins+1];
+ fgIntegral[0] = 0;
+ Int_t bin;
+ for(bin=0;bin<nbins;bin++) {
+ tG->GetEvent(bin);
+ fgIntegral[bin+1] = fgIntegral[bin] + cell[0];
+ }
+ // Normalize integral to 1
+ if (fgIntegral[nbins] == 0 ) {
+ return 0;
+ }
+ for (bin=1;bin<=nbins;bin++) fgIntegral[bin] /= fgIntegral[nbins];
+
+ return fgIntegral[nbins];
+}
+
+//____________________________________________________________________________________
+void AliGenCorrHF::GetQuarkPair(TFile* fG, Double_t* fInt, Double_t &y1, Double_t &y2, Double_t &pt1, Double_t &pt2, Double_t &dphi)
+ // modification of ROOT's TH3::GetRandom3 for 5D
+{
+ // Read QQbar kinematical 5D grid's cell coordinates
+ Int_t* cell = new Int_t[6]; // cell[6]={wght,iy1,iy2,ipt1,ipt2,idph}
+ TTree* tG = (TTree*) fG->Get("tGqq");
+ tG->GetBranch("cell")->SetAddress(cell);
+ Int_t nbins = tG->GetEntries();
+ Double_t rand[6];
+ gRandom->RndmArray(6,rand);
+ Int_t ibin = TMath::BinarySearch(nbins,fInt,rand[0]);
+ tG->GetEvent(ibin);
+ y1 = fgy[cell[1]] + (fgy[cell[1]+1]-fgy[cell[1]])*rand[1];
+ y2 = fgy[cell[2]] + (fgy[cell[2]+1]-fgy[cell[2]])*rand[2];
+ pt1 = fgpt[cell[3]] + (fgpt[cell[3]+1]-fgpt[cell[3]])*rand[3];
+ pt2 = fgpt[cell[4]] + (fgpt[cell[4]+1]-fgpt[cell[4]])*rand[4];
+ dphi = fgdph[cell[5]]+ (fgdph[cell[5]+1]-fgdph[cell[5]])*rand[5];
+}
+
+//____________________________________________________________________________________
+void AliGenCorrHF::GetHadronPair(TFile* fG, Int_t idq, Double_t y1, Double_t y2, Double_t pt1, Double_t pt2, Int_t &id3, Int_t &id4, Double_t &pz3, Double_t &pz4, Double_t &pt3, Double_t &pt4)
+{
+ // Generate a hadron pair
+ Int_t (*fIpParaFunc )(TRandom*);//Pointer to particle type parametrisation function
+ fIpParaFunc = IpCharm;
+ Double_t mq = 1.2; // c & b quark masses (used in AliPythia)
+ if (idq == 5) {
+ fIpParaFunc = IpBeauty;
+ mq = 4.75;
+ }
+ Double_t z11, z12, z21, z22, pz1, pz2, e1, e2, mh, ptemp, rand[2];
+ char tag[100];
+ TH2F *h2h[12], *h2s[12]; // hard & soft Fragmentation Functions
+ for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
+ sprintf(tag,"h2h_pt%d",ipt);
+ h2h[ipt] = (TH2F*) fG->Get(tag);
+ sprintf(tag,"h2s_pt%d",ipt);
+ h2s[ipt] = (TH2F*) fG->Get(tag);
+ }
+
+ if (y1*y2 < 0) {
+ for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
+ if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
+ h2h[ipt]->GetRandom2(z11, z21);
+ if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
+ h2h[ipt]->GetRandom2(z12, z22);
+ }
+ }
+ else {
+ if (TMath::Abs(y1) > TMath::Abs(y2)) {
+ for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
+ if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
+ h2h[ipt]->GetRandom2(z11, z21);
+ if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
+ h2s[ipt]->GetRandom2(z12, z22);
+ }
+ }
+ else {
+ for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
+ if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
+ h2s[ipt]->GetRandom2(z11, z21);
+ if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
+ h2h[ipt]->GetRandom2(z12, z22);
+ }
+ }
+ }
+ gRandom->RndmArray(2,rand);
+ ptemp = TMath::Sqrt(pt1*pt1 + mq*mq);
+ pz1 = ptemp*TMath::SinH(y1);
+ e1 = ptemp*TMath::CosH(y1);
+ ptemp = TMath::Sqrt(pt2*pt2 + mq*mq);
+ pz2 = ptemp*TMath::SinH(y2);
+ e2 = ptemp*TMath::CosH(y2);
+
+ id3 = fIpParaFunc(gRandom);
+ mh = TDatabasePDG::Instance()->GetParticle(id3)->Mass();
+ ptemp = z11*z21*(e1*e1-pz1*pz1) - mh*mh;
+ pt3 = (idq-3)*rand[0]; // some smearing at low pt, try better
+ if (ptemp > 0) pt3 = TMath::Sqrt(ptemp);
+ if (pz1 > 0) pz3 = (z11*(e1 + pz1) - z21*(e1 - pz1)) / 2;
+ else pz3 = (z21*(e1 + pz1) - z11*(e1 - pz1)) / 2;
+ e1 = TMath::Sqrt(pz3*pz3 + pt3*pt3 + mh*mh);
+
+ id4 = - fIpParaFunc(gRandom);
+ mh = TDatabasePDG::Instance()->GetParticle(id4)->Mass();
+ ptemp = z12*z22*(e2*e2-pz2*pz2) - mh*mh;
+ pt4 = (idq-3)*rand[1]; // some smearing at low pt, try better
+ if (ptemp > 0) pt4 = TMath::Sqrt(ptemp);
+ if (pz2 > 0) pz4 = (z12*(e2 + pz2) - z22*(e2 - pz2)) / 2;
+ else pz4 = (z22*(e2 + pz2) - z12*(e2 - pz2)) / 2;
+ e2 = TMath::Sqrt(pz4*pz4 + pt4*pt4 + mh*mh);
+
+ // small corr. instead of using Frag. Func. depending on yQ (in addition to ptQ)
+ Float_t ycorr = 0.2, y3, y4;
+ gRandom->RndmArray(2,rand);
+ y3 = 0.5 * TMath::Log((e1 + pz3 + 1.e-13)/(e1 - pz3 + 1.e-13));
+ y4 = 0.5 * TMath::Log((e2 + pz4 + 1.e-13)/(e2 - pz4 + 1.e-13));
+ if(TMath::Abs(y3)<ycorr && TMath::Abs(y4)<ycorr && rand[0]>0.5) {
+ ptemp = TMath::Sqrt(e1*e1 - pz3*pz3);
+ y3 = 4*(1 - 2*rand[1]);
+ pz3 = ptemp*TMath::SinH(y3);
+ pz4 = pz3;
+ }
+}