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 *
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12 * about the suitability of this software for any purpose. It is *
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14 **************************************************************************/
18 // Class to generate correlated Heavy Flavor hadron pairs (one or several pairs
19 // per event) using paramtrized kinematics of quark pairs from some generator
20 // and quark fragmentation functions.
21 // Is a generalisation of AliGenParam class for correlated pairs of hadrons.
22 // In this version quark pairs and fragmentation functions are obtained from
23 // Pythia6.124 using 100K events generated with kCharmppMNRwmi&kBeautyppMNRwmi
24 // in pp collisions at 14 TeV.
25 // Decays are performed by Pythia. Used AliRoot version: v4-04-Release
26 // Author: S. Grigoryan, LPC Clermont-Fd & YerPhI, Smbat.Grigoryan@cern.ch
27 // July 07: added quarks in the stack (B. Vulpescu)
28 //-------------------------------------------------------------------------
29 // How it works (for the given flavor):
31 // 1) Reads QQbar kinematical grid from the Input file and generates
32 // quark pairs according to the weights of the cells.
33 // It is a 5D grid in y1,y2,pt1,pt2 and deltaphi, with occupancy weights
34 // of the cells obtained from Pythia (see details in GetQuarkPair).
35 // 2) Reads "soft" and "hard" fragmentation functions (12 2D-histograms each,
36 // for 12 pt bins) from the Input file, applies to quarks and produces hadrons
37 // (only lower states, with proportions of species obtained from Pythia).
38 // Fragmentation functions are the same for all hadron species and depend
39 // on 2 variables - light cone energy-momentum fractions:
40 // z1=(E_H + Pz_H)/(E_Q + Pz_Q), z2=(E_H - Pz_H)/(E_Q - Pz_Q).
41 // "soft" & "hard" FFs correspond to "slower" & "faster" quark of a pair
42 // (see details in GetHadronPair).
43 // 3) Decays the hadrons and saves all the particles in the event stack in the
44 // following order: HF hadron from Q, then its decay products, then HF hadron
45 // from Qbar, then its decay productes, then next HF hadon pair (if any)
46 // in the same way, etc...
47 // 4) It is fast, e.g., generates the same number of events with a beauty pair
48 // ~15 times faster than AliGenPythia with kBeautyppMNRwmi (w/o tracking)
50 // An Input file for each quark flavor is included in EVGEN/dataCorrHF/
51 // One can use also user-defined Input files.
53 // More details could be found in my presentation at DiMuonNet Workshop, Dec 2006:
54 // http://www-dapnia.cea.fr/Sphn/Alice/DiMuonNet
55 // and will be published in an Internal Note.
57 //-------------------------------------------------------------------------
60 // add the following typical lines in Config.C
62 if (!strcmp(option,"corr")) {
63 // Example for correlated charm or beauty hadron pair production
65 // AliGenCorrHF *gener = new AliGenCorrHF(1, 4); // for charm, 1 pair per event
66 AliGenCorrHF *gener = new AliGenCorrHF(1, 5); // for beauty, 1 pair per event
68 gener->SetMomentumRange(0,9999);
69 gener->SetCutOnChild(0); // 1/0 means cuts on children enable/disable
70 gener->SetChildThetaRange(171.0,178.0);
71 gener->SetOrigin(0,0,0); //vertex position
72 gener->SetSigma(0,0,0); //Sigma in (X,Y,Z) (cm) on IP position
73 gener->SetForceDecay(kSemiMuonic);
74 gener->SetTrackingFlag(0);
78 // and in aliroot do e.g. gAlice->Run(10,"Config.C") to produce 10 events.
79 // One can include AliGenCorrHF in an AliGenCocktail generator.
80 //--------------------------------------------------------------------------
82 #include <Riostream.h>
84 #include <TClonesArray.h>
85 #include <TDatabasePDG.h>
88 #include <TLorentzVector.h>
90 #include <TParticle.h>
91 #include <TParticlePDG.h>
95 #include <TVirtualMC.h>
98 #include "AliGenCorrHF.h"
100 #include "AliConst.h"
101 #include "AliDecayer.h"
104 #include "AliGenEventHeader.h"
106 ClassImp(AliGenCorrHF)
110 <img src="picts/AliGenCorrHF.gif">
114 Double_t AliGenCorrHF::fgdph[19] = {0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180};
115 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};
116 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};
117 Int_t AliGenCorrHF::fgnptbins = 12;
118 Double_t AliGenCorrHF::fgptbmin[12] = {0, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 9};
119 Double_t AliGenCorrHF::fgptbmax[12] = {0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 9, 100};
121 Double_t* AliGenCorrHF::fgIntegral = 0;
123 //____________________________________________________________
124 AliGenCorrHF::AliGenCorrHF():
132 // Default constructor
135 //____________________________________________________________
136 AliGenCorrHF::AliGenCorrHF(Int_t npart, Int_t param):
143 // fDecayer(new AliDecayerPythia())
146 // Constructor using number of particles, quark type & default InputFile
148 if (fQuark != 5) fQuark = 4;
149 fFileName = "$ALICE_ROOT/EVGEN/dataCorrHF/CharmppMNRwmiCorr100K.root";
150 if (fQuark == 5) fFileName = "$ALICE_ROOT/EVGEN/dataCorrHF/BeautyppMNRwmiCorr100K.root";
153 fTitle= "Generator for correlated pairs of HF hadrons";
156 for (Int_t i=0; i<5; i++) fChildSelect[i]=0;
159 SetChildMomentumRange();
162 SetChildThetaRange();
165 //___________________________________________________________________
166 AliGenCorrHF::AliGenCorrHF(char* tname, Int_t npart, Int_t param):
173 // fDecayer(new AliDecayerPythia())
176 // Constructor using number of particles, quark type & user-defined InputFile
178 if (fQuark != 5) fQuark = 4;
179 fName = "UserDefined";
180 fTitle= "Generator for correlated pairs of HF hadrons";
183 for (Int_t i=0; i<5; i++) fChildSelect[i]=0;
186 SetChildMomentumRange();
189 SetChildThetaRange();
192 //____________________________________________________________
193 AliGenCorrHF::~AliGenCorrHF()
199 //____________________________________________________________
200 void AliGenCorrHF::Init()
204 AliInfo(Form(" QQbar kinematics and fragm. functions from: %s",fFileName.Data() ));
205 fFile = TFile::Open(fFileName.Data());
206 if(!fFile->IsOpen()){
207 AliError(Form("Could not open file %s",fFileName.Data() ));
210 ComputeIntegral(fFile);
212 fParentWeight = 1./fNpart; // fNpart is number of HF-hadron pairs
214 // particle decay related initialization
216 if (gMC) fDecayer = gMC->GetDecayer();
217 fDecayer->SetForceDecay(fForceDecay);
223 //____________________________________________________________
224 void AliGenCorrHF::Generate()
227 // Generate fNpart of correlated HF hadron pairs per event
228 // in the the desired theta and momentum windows (phi = 0 - 2pi).
231 // Reinitialize decayer
233 fDecayer->SetForceDecay(fForceDecay);
237 Float_t polar[3]= {0,0,0}; // Polarisation of the parent particle (for GEANT tracking)
238 Float_t origin0[3]; // Origin of the generated parent particle (for GEANT tracking)
239 Float_t pt, pl, ptot; // Transverse, logitudinal and total momenta of the parent particle
240 Float_t phi, theta; // Phi and theta spherical angles of the parent particle momentum
241 Float_t p[3], pc[3], och[3];// Momentum, polarisation and origin of the children particles from lujet
242 Int_t nt, i, j, ipa, ihadron[2], iquark[2];
243 Float_t wgtp, wgtch, random[6];
244 Float_t pq[2][3]; // Momenta of the two quarks
245 Int_t ntq[2] = {-1, -1};
246 Double_t tanhy2, qm = 0;
248 Double_t dphi=0, ptq[2], yq[2], pth[2], plh[2], ph[2], phih[2], phiq[2];
249 for (i=0; i<2; i++) {
260 // same quarks mass as in the fragmentation functions
261 if (fQuark == 4) qm = 1.20;
264 static TClonesArray *particles;
266 if(!particles) particles = new TClonesArray("TParticle",1000);
268 TDatabasePDG *pDataBase = TDatabasePDG::Instance();
271 // Calculating vertex position per event
272 for (j=0;j<3;j++) origin0[j]=fOrigin[j];
273 if(fVertexSmear==kPerEvent) {
275 for (j=0;j<3;j++) origin0[j]=fVertex[j];
280 // Generating fNpart particles
283 while (ipa<2*fNpart) {
285 GetQuarkPair(fFile, fgIntegral, yq[0], yq[1], ptq[0], ptq[1], dphi);
287 GetHadronPair(fFile, fQuark, yq[0], yq[1], ptq[0], ptq[1], ihadron[0], ihadron[1], plh[0], plh[1], pth[0], pth[1]);
289 // Cuts from AliGenerator
292 theta=TMath::ATan2(pth[0],plh[0]);
293 if(theta<fThetaMin || theta>fThetaMax) continue;
294 theta=TMath::ATan2(pth[1],plh[1]);
295 if(theta<fThetaMin || theta>fThetaMax) continue;
298 ph[0]=TMath::Sqrt(pth[0]*pth[0]+plh[0]*plh[0]);
299 if (ph[0]<fPMin || ph[0]>fPMax) continue;
300 ph[1]=TMath::Sqrt(pth[1]*pth[1]+plh[1]*plh[1]);
301 if (ph[1]<fPMin || ph[1]>fPMax) continue;
303 // Add the quarks in the stack
305 phiq[0] = Rndm()*k2PI;
307 phiq[1] = phiq[0] + dphi*kDegrad;
309 phiq[1] = phiq[0] - dphi*kDegrad;
311 if (phiq[1] > k2PI) phiq[1] -= k2PI;
312 if (phiq[1] < 0 ) phiq[1] += k2PI;
319 TVector2 qvect1 = TVector2();
320 TVector2 qvect2 = TVector2();
321 qvect1.SetMagPhi(ptq[0],phiq[0]);
322 qvect2.SetMagPhi(ptq[1],phiq[1]);
323 pq[0][0] = qvect1.Px();
324 pq[0][1] = qvect1.Py();
325 pq[1][0] = qvect2.Px();
326 pq[1][1] = qvect2.Py();
329 tanhy2 = TMath::TanH(yq[0]);
331 pq[0][2] = TMath::Sqrt((ptq[0]*ptq[0]+qm*qm)*tanhy2/(1-tanhy2));
332 pq[0][2] = TMath::Sign((Double_t)pq[0][2],yq[0]);
333 tanhy2 = TMath::TanH(yq[1]);
335 pq[1][2] = TMath::Sqrt((ptq[1]*ptq[1]+qm*qm)*tanhy2/(1-tanhy2));
336 pq[1][2] = TMath::Sign((Double_t)pq[1][2],yq[1]);
338 // Here we assume that |phi_H1 - phi_H2| = |phi_Q1 - phi_Q2| = dphi
339 // which is a good approximation for heavy flavors in Pythia
340 // ... moreover, same phi angles as for the quarks ...
345 for (Int_t ihad = 0; ihad < 2; ihad++) {
349 Int_t iPart = ihadron[ihad];
350 fChildWeight=(fDecayer->GetPartialBranchingRatio(iPart))*fParentWeight;
353 TParticlePDG *particle = pDataBase->GetParticle(iPart);
354 Float_t am = particle->Mass();
358 ptot=TMath::Sqrt(pt*pt+pl*pl);
360 p[0]=pt*TMath::Cos(phi);
361 p[1]=pt*TMath::Sin(phi);
364 if(fVertexSmear==kPerTrack) {
368 fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
369 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
373 // Looking at fForceDecay :
374 // if fForceDecay != none Primary particle decays using
375 // AliPythia and children are tracked by GEANT
377 // if fForceDecay == none Primary particle is tracked by GEANT
378 // (In the latest, make sure that GEANT actually does all the decays you want)
381 if (fForceDecay != kNoDecay) {
382 // Using lujet to decay particle
383 Float_t energy=TMath::Sqrt(ptot*ptot+am*am);
384 TLorentzVector pmom(p[0], p[1], p[2], energy);
385 fDecayer->Decay(iPart,&pmom);
387 // select decay particles
388 Int_t np=fDecayer->ImportParticles(particles);
390 // Selecting GeometryAcceptance for particles fPdgCodeParticleforAcceptanceCut;
391 if (fGeometryAcceptance)
392 if (!CheckAcceptanceGeometry(np,particles)) continue;
394 Int_t* pFlag = new Int_t[np];
395 Int_t* pParent = new Int_t[np];
396 Int_t* pSelected = new Int_t[np];
397 Int_t* trackIt = new Int_t[np];
399 for (i=0; i<np; i++) {
406 TParticle* iparticle = (TParticle *) particles->At(0);
408 for (i = 1; i<np ; i++) {
410 iparticle = (TParticle *) particles->At(i);
411 Int_t kf = iparticle->GetPdgCode();
412 Int_t ks = iparticle->GetStatusCode();
416 ipF = iparticle->GetFirstDaughter();
417 ipL = iparticle->GetLastDaughter();
418 if (ipF > 0) for (j=ipF-1; j<ipL; j++) pFlag[j]=1;
422 // flag decay products of particles with long life-time (c tau > .3 mum)
425 //TParticlePDG *particle = pDataBase->GetParticle(kf);
427 Double_t lifeTime = fDecayer->GetLifetime(kf);
428 //Double_t mass = particle->Mass();
429 //Double_t width = particle->Width();
430 if (lifeTime > (Double_t) fMaxLifeTime) {
431 ipF = iparticle->GetFirstDaughter();
432 ipL = iparticle->GetLastDaughter();
433 if (ipF > 0) for (j=ipF-1; j<ipL; j++) pFlag[j]=1;
442 if (ChildSelected(TMath::Abs(kf)) || fForceDecay == kAll && trackIt[i])
445 pc[0]=iparticle->Px();
446 pc[1]=iparticle->Py();
447 pc[2]=iparticle->Pz();
448 Bool_t childok = KinematicSelection(iparticle, 1);
459 } // if child selection
461 } // decay particle loop
462 } // if decay products
465 if ((fCutOnChild && ncsel >0) || !fCutOnChild){
470 PushTrack(0, -1, iquark[ihad], pq[ihad], origin0, polar, 0, kPPrimary, nt, wgtp);
474 PushTrack(0, ntq[ihad], iPart, p, origin0, polar, 0, kPDecay, nt, wgtp);
482 for (i = 1; i < np; i++) {
484 TParticle* iparticle = (TParticle *) particles->At(i);
485 Int_t kf = iparticle->GetPdgCode();
486 Int_t ipa = iparticle->GetFirstMother()-1;
488 och[0] = origin0[0]+iparticle->Vx()/10;
489 och[1] = origin0[1]+iparticle->Vy()/10;
490 och[2] = origin0[2]+iparticle->Vz()/10;
491 pc[0] = iparticle->Px();
492 pc[1] = iparticle->Py();
493 pc[2] = iparticle->Pz();
496 iparent = pParent[ipa];
501 PushTrack(fTrackIt*trackIt[i], iparent, kf,
503 0, kPDecay, nt, wgtch);
511 if (pFlag) delete[] pFlag;
512 if (pParent) delete[] pParent;
513 if (pSelected) delete[] pSelected;
514 if (trackIt) delete[] trackIt;
515 } // kinematic selection
516 else // nodecay option, so parent will be tracked by GEANT (pions, kaons, eta, omegas, baryons)
519 PushTrack(fTrackIt,-1,iPart,p,origin0,polar,0,kPPrimary,nt,wgtp);
525 } // hadron pair loop
528 SetHighWaterMark(nt);
530 AliGenEventHeader* header = new AliGenEventHeader("CorrHF");
531 header->SetPrimaryVertex(fVertex);
532 header->SetNProduced(fNprimaries);
536 //____________________________________________________________________________________
537 Int_t AliGenCorrHF::IpCharm(TRandom* ran)
539 // Composition of lower state charm hadrons, containing a c-quark
541 Int_t ip; // +- 411,421,431,4122,4132,4232,4332
542 random = ran->Rndm();
543 // Rates from Pythia6.214 using 100Kevents with kPyCharmppMNRwmi at 14 TeV.
545 if (random < 0.6027) {
547 } else if (random < 0.7962) {
549 } else if (random < 0.9127) {
551 } else if (random < 0.9899) {
553 } else if (random < 0.9948) {
555 } else if (random < 0.9999) {
564 Int_t AliGenCorrHF::IpBeauty(TRandom* ran)
566 // Composition of lower state beauty hadrons, containing a b-quark
568 Int_t ip; // +- 511,521,531,5122,5132,5232,5332
569 random = ran->Rndm();
570 // Rates from Pythia6.214 using 100Kevents with kPyBeautyppMNRwmi at 14 TeV.
571 // B-Bbar mixing will be done by Pythia at the decay point
572 if (random < 0.3965) {
574 } else if (random < 0.7930) {
576 } else if (random < 0.9112) {
578 } else if (random < 0.9887) {
580 } else if (random < 0.9943) {
582 } else if (random < 0.9999) {
591 //____________________________________________________________________________________
592 Double_t AliGenCorrHF::ComputeIntegral(TFile* fG) // needed by GetQuarkPair
594 // Read QQbar kinematical 5D grid's cell occupancy weights
595 Int_t cell[6]; // cell[6]={wght,iy1,iy2,ipt1,ipt2,idph}
596 TTree* tG = (TTree*) fG->Get("tGqq");
597 tG->GetBranch("cell")->SetAddress(&cell);
598 Int_t nbins = tG->GetEntries();
600 // delete previously computed integral (if any)
601 if(fgIntegral) delete [] fgIntegral;
603 fgIntegral = new Double_t[nbins+1];
606 for(bin=0;bin<nbins;bin++) {
608 fgIntegral[bin+1] = fgIntegral[bin] + cell[0];
610 // Normalize integral to 1
611 if (fgIntegral[nbins] == 0 ) {
614 for (bin=1;bin<=nbins;bin++) fgIntegral[bin] /= fgIntegral[nbins];
616 return fgIntegral[nbins];
619 //____________________________________________________________________________________
620 void AliGenCorrHF::GetQuarkPair(TFile* fG, Double_t* fInt, Double_t &y1, Double_t &y2, Double_t &pt1, Double_t &pt2, Double_t &dphi)
621 // modification of ROOT's TH3::GetRandom3 for 5D
623 // Read QQbar kinematical 5D grid's cell coordinates
624 Int_t cell[6]; // cell[6]={wght,iy1,iy2,ipt1,ipt2,idph}
625 TTree* tG = (TTree*) fG->Get("tGqq");
626 tG->GetBranch("cell")->SetAddress(&cell);
627 Int_t nbins = tG->GetEntries();
629 gRandom->RndmArray(6,rand);
630 Int_t ibin = TMath::BinarySearch(nbins,fInt,rand[0]);
632 y1 = fgy[cell[1]] + (fgy[cell[1]+1]-fgy[cell[1]])*rand[1];
633 y2 = fgy[cell[2]] + (fgy[cell[2]+1]-fgy[cell[2]])*rand[2];
634 pt1 = fgpt[cell[3]] + (fgpt[cell[3]+1]-fgpt[cell[3]])*rand[3];
635 pt2 = fgpt[cell[4]] + (fgpt[cell[4]+1]-fgpt[cell[4]])*rand[4];
636 dphi = fgdph[cell[5]]+ (fgdph[cell[5]+1]-fgdph[cell[5]])*rand[5];
639 //____________________________________________________________________________________
640 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)
642 // Generate a hadron pair
643 Int_t (*fIpParaFunc )(TRandom*);//Pointer to particle type parametrisation function
644 fIpParaFunc = IpCharm;
645 Double_t mq = 1.2; // c & b quark masses (used in AliPythia)
647 fIpParaFunc = IpBeauty;
650 Double_t z11, z12, z21, z22, pz1, pz2, e1, e2, mh, ptemp, rand[2];
652 TH2F *h2h[12], *h2s[12]; // hard & soft Fragmentation Functions
653 for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
654 sprintf(tag,"h2h_pt%d",ipt);
655 h2h[ipt] = (TH2F*) fG->Get(tag);
656 sprintf(tag,"h2s_pt%d",ipt);
657 h2s[ipt] = (TH2F*) fG->Get(tag);
661 for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
662 if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
663 h2h[ipt]->GetRandom2(z11, z21);
664 if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
665 h2h[ipt]->GetRandom2(z12, z22);
669 if (TMath::Abs(y1) > TMath::Abs(y2)) {
670 for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
671 if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
672 h2h[ipt]->GetRandom2(z11, z21);
673 if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
674 h2s[ipt]->GetRandom2(z12, z22);
678 for (Int_t ipt = 0; ipt<fgnptbins; ipt++) {
679 if(pt1 >= fgptbmin[ipt] && pt1 < fgptbmax[ipt])
680 h2s[ipt]->GetRandom2(z11, z21);
681 if(pt2 >= fgptbmin[ipt] && pt2 < fgptbmax[ipt])
682 h2h[ipt]->GetRandom2(z12, z22);
686 gRandom->RndmArray(2,rand);
687 ptemp = TMath::Sqrt(pt1*pt1 + mq*mq);
688 pz1 = ptemp*TMath::SinH(y1);
689 e1 = ptemp*TMath::CosH(y1);
690 ptemp = TMath::Sqrt(pt2*pt2 + mq*mq);
691 pz2 = ptemp*TMath::SinH(y2);
692 e2 = ptemp*TMath::CosH(y2);
694 id3 = fIpParaFunc(gRandom);
695 mh = TDatabasePDG::Instance()->GetParticle(id3)->Mass();
696 ptemp = z11*z21*(e1*e1-pz1*pz1) - mh*mh;
697 pt3 = (idq-3)*rand[0]; // some smearing at low pt, try better
698 if (ptemp > 0) pt3 = TMath::Sqrt(ptemp);
699 if (pz1 > 0) pz3 = (z11*(e1 + pz1) - z21*(e1 - pz1)) / 2;
700 else pz3 = (z21*(e1 + pz1) - z11*(e1 - pz1)) / 2;
701 e1 = TMath::Sqrt(pz3*pz3 + pt3*pt3 + mh*mh);
703 id4 = - fIpParaFunc(gRandom);
704 mh = TDatabasePDG::Instance()->GetParticle(id4)->Mass();
705 ptemp = z12*z22*(e2*e2-pz2*pz2) - mh*mh;
706 pt4 = (idq-3)*rand[1]; // some smearing at low pt, try better
707 if (ptemp > 0) pt4 = TMath::Sqrt(ptemp);
708 if (pz2 > 0) pz4 = (z12*(e2 + pz2) - z22*(e2 - pz2)) / 2;
709 else pz4 = (z22*(e2 + pz2) - z12*(e2 - pz2)) / 2;
710 e2 = TMath::Sqrt(pz4*pz4 + pt4*pt4 + mh*mh);
712 // small corr. instead of using Frag. Func. depending on yQ (in addition to ptQ)
713 Float_t ycorr = 0.2, y3, y4;
714 gRandom->RndmArray(2,rand);
715 y3 = 0.5 * TMath::Log((e1 + pz3 + 1.e-13)/(e1 - pz3 + 1.e-13));
716 y4 = 0.5 * TMath::Log((e2 + pz4 + 1.e-13)/(e2 - pz4 + 1.e-13));
717 if(TMath::Abs(y3)<ycorr && TMath::Abs(y4)<ycorr && rand[0]>0.5) {
718 ptemp = TMath::Sqrt(e1*e1 - pz3*pz3);
719 y3 = 4*(1 - 2*rand[1]);
720 pz3 = ptemp*TMath::SinH(y3);