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 // Base class for generators using external MC generators.
19 // For example AliGenPythia using Pythia.
20 // Provides basic functionality: setting of kinematic cuts on
21 // decay products and particle selection.
22 // andreas.morsch@cern.ch
24 #include <TClonesArray.h>
27 #include <TParticle.h>
28 #include <TLorentzVector.h>
32 #include "AliGenEventHeader.h"
34 #include "AliGeometry.h"
35 #include "AliDecayer.h"
41 fParticles("TParticle", 1000),
50 fChildPhiMax(2. * TMath::Pi()),
52 fChildThetaMax(TMath::Pi()),
60 fGeometryAcceptance(0),
61 fPdgCodeParticleforAcceptanceCut(0),
62 fNumberOfAcceptedParticles(0),
65 // Default Constructor
74 AliGenMC::AliGenMC(Int_t npart)
76 fParticles("TParticle", 1000),
85 fChildPhiMax(2. * TMath::Pi()),
87 fChildThetaMax(TMath::Pi()),
95 fGeometryAcceptance(0),
96 fPdgCodeParticleforAcceptanceCut(0),
97 fNumberOfAcceptedParticles(0),
108 for (Int_t i=0; i<8; i++) fParentSelect[i]=fChildSelect[i]=0;
111 AliGenMC::~AliGenMC()
116 void AliGenMC::Init()
120 switch (fForceDecay) {
121 case kBSemiElectronic:
122 case kSemiElectronic:
124 case kBJpsiDiElectron:
125 case kBPsiPrimeDiElectron:
128 fChildSelect[0] = kElectron;
136 case kBPsiPrimeDiMuon:
140 case kWToCharmToMuon:
143 fChildSelect[0]=kMuonMinus;
148 case kHadronicDWithout4Bodies:
149 fChildSelect[0]=kPiPlus;
150 fChildSelect[1]=kKPlus;
153 fChildSelect[0]=kKPlus;
156 case kBJpsiUndecayed:
157 fChildSelect[0]= 443;
159 case kChiToJpsiGammaToMuonMuon:
163 case kChiToJpsiGammaToElectronElectron:
168 fChildSelect[0]= kProton;
169 fChildSelect[1]= 211;
171 case kPsiPrimeJpsiDiElectron:
172 fChildSelect[0]= 211;
176 fChildSelect[0] = kGamma;
189 if (fZTarget != 0 && fAProjectile != 0)
191 fDyBoost = - 0.5 * TMath::Log(Double_t(fZProjectile) * Double_t(fATarget) /
192 (Double_t(fZTarget) * Double_t(fAProjectile)));
197 Bool_t AliGenMC::ParentSelected(Int_t ip) const
199 // True if particle is in list of parent particles to be selected
200 for (Int_t i=0; i<8; i++)
202 if (fParentSelect.At(i) == ip) return kTRUE;
207 Bool_t AliGenMC::ChildSelected(Int_t ip) const
209 // True if particle is in list of decay products to be selected
210 for (Int_t i=0; i<5; i++)
212 if (fChildSelect.At(i) == ip) return kTRUE;
217 Bool_t AliGenMC::KinematicSelection(const TParticle *particle, Int_t flag) const
219 // Perform kinematic selection
220 Double_t pz = particle->Pz();
221 Double_t pt = particle->Pt();
222 Double_t p = particle->P();
223 Double_t theta = particle->Theta();
224 Double_t mass = particle->GetCalcMass();
225 Double_t mt2 = pt * pt + mass * mass;
226 Double_t phi = particle->Phi();
227 Double_t e = particle->Energy();
230 e = TMath::Sqrt(p * p + mass * mass);
235 if (TMath::Abs(pz) < e) {
236 y = 0.5*TMath::Log((e+pz)/(e-pz));
242 y0 = 0.5*TMath::Log((e+TMath::Abs(pz))*(e+TMath::Abs(pz))/mt2);
244 if (TMath::Abs(y) < 1.e10) {
251 y = (pz < 0) ? -y0 : y0;
255 // Primary particle cuts
257 // transverse momentum cut
258 if (pt > fPtMax || pt < fPtMin) {
259 // printf("\n failed pt cut %f %f %f \n",pt,fPtMin,fPtMax);
264 if (p > fPMax || p < fPMin) {
265 // printf("\n failed p cut %f %f %f \n",p,fPMin,fPMax);
270 if (theta > fThetaMax || theta < fThetaMin) {
271 // printf("\n failed theta cut %f %f %f \n",theta,fThetaMin,fThetaMax);
276 if (y > fYMax || y < fYMin) {
277 // printf("\n failed y cut %f %f %f \n",y,fYMin,fYMax);
282 if (phi > fPhiMax || phi < fPhiMin) {
283 // printf("\n failed phi cut %f %f %f \n",phi,fPhiMin,fPhiMax);
288 // Decay product cuts
290 // transverse momentum cut
291 if (pt > fChildPtMax || pt < fChildPtMin) {
292 // printf("\n failed pt cut %f %f %f \n",pt,fChildPtMin,fChildPtMax);
297 if (p > fChildPMax || p < fChildPMin) {
298 // printf("\n failed p cut %f %f %f \n",p,fChildPMin,fChildPMax);
303 if (theta > fChildThetaMax || theta < fChildThetaMin) {
304 // printf("\n failed theta cut %f %f %f \n",theta,fChildThetaMin,fChildThetaMax);
309 if (y > fChildYMax || y < fChildYMin) {
310 // printf("\n failed y cut %f %f %f \n",y,fChildYMin,fChildYMax);
315 if (phi > fChildPhiMax || phi < fChildPhiMin) {
316 // printf("\n failed phi cut %f %f %f \n",phi,fChildPhiMin,fChildPhiMax);
324 Bool_t AliGenMC::CheckAcceptanceGeometry(Int_t np, TClonesArray* particles)
326 // Check the geometrical acceptance for particle.
329 Int_t numberOfPdgCodeParticleforAcceptanceCut = 0;
330 Int_t numberOfAcceptedPdgCodeParticleforAcceptanceCut = 0;
331 TParticle * particle;
333 for (i = 0; i < np; i++) {
334 particle = (TParticle *) particles->At(i);
335 if( TMath::Abs( particle->GetPdgCode() ) == TMath::Abs( fPdgCodeParticleforAcceptanceCut ) ) {
336 numberOfPdgCodeParticleforAcceptanceCut++;
337 if (fGeometryAcceptance->Impact(particle)) numberOfAcceptedPdgCodeParticleforAcceptanceCut++;
340 if ( numberOfAcceptedPdgCodeParticleforAcceptanceCut > (fNumberOfAcceptedParticles-1) )
348 Int_t AliGenMC::CheckPDGCode(Int_t pdgcode) const
351 // If the particle is in a diffractive state, then take action accordingly
356 //rho_diff0 -- difficult to translate, return rho0
359 //pi_diffr+ -- change to pi+
362 //omega_di0 -- change to omega0
365 //phi_diff0 -- return phi0
368 //J/psi_di0 -- return J/psi
371 //n_diffr -- return neutron
374 //p_diffr+ -- return proton
377 //non diffractive state -- return code unchanged
381 void AliGenMC::Boost()
384 // Boost cms into LHC lab frame
387 Double_t beta = TMath::TanH(fDyBoost);
388 Double_t gamma = 1./TMath::Sqrt((1.-beta)*(1.+beta));
389 Double_t gb = gamma * beta;
391 // printf("\n Boosting particles to lab frame %f %f %f", fDyBoost, beta, gamma);
394 Int_t np = fParticles.GetEntriesFast();
395 for (i = 0; i < np; i++)
397 TParticle* iparticle = (TParticle*) fParticles.At(i);
399 Double_t e = iparticle->Energy();
400 Double_t px = iparticle->Px();
401 Double_t py = iparticle->Py();
402 Double_t pz = iparticle->Pz();
404 Double_t eb = gamma * e - gb * pz;
405 Double_t pzb = -gb * e + gamma * pz;
407 iparticle->SetMomentum(px, py, pzb, eb);
411 void AliGenMC::BeamCrossAngle()
413 // Applies a boost in the y-direction in order to take into account the
414 // beam crossing angle
416 Double_t thetaPr0, phiPr0, pyPr2, pzPr2;
419 thetaPr0 = fXingAngleY / 2.;
422 // Momentum of the CMS system
423 pyPr2 = TMath::Sqrt(fEnergyCMS * fEnergyCMS/ 4 - 0.938 * 0.938) * TMath::Sin(thetaPr0);
424 pzPr2 = TMath::Sqrt(fEnergyCMS * fEnergyCMS/ 4 - 0.938 * 0.938) * TMath::Cos(thetaPr0);
426 TLorentzVector proj1Vect, proj2Vect, projVect;
427 proj1Vect.SetPxPyPzE(0., pyPr2, pzPr2, fEnergyCMS/2);
428 proj2Vect.SetPxPyPzE(0., pyPr2,-pzPr2, fEnergyCMS/2);
429 projVect = proj1Vect + proj2Vect;
430 beta=(1. / projVect.E()) * (projVect.Vect());
433 Int_t np = fParticles.GetEntriesFast();
434 for (i = 0; i < np; i++)
436 TParticle* iparticle = (TParticle*) fParticles.At(i);
438 Double_t e = iparticle->Energy();
439 Double_t px = iparticle->Px();
440 Double_t py = iparticle->Py();
441 Double_t pz = iparticle->Pz();
443 TLorentzVector partIn;
444 partIn.SetPxPyPzE(px,py,pz,e);
446 iparticle->SetMomentum(partIn.Px(),partIn.Py(),partIn.Pz(),partIn.E());
451 void AliGenMC::AddHeader(AliGenEventHeader* header)
453 // Passes header either to the container or to gAlice
455 header->SetName(fName);
456 fContainer->AddHeader(header);
458 gAlice->SetGenEventHeader(header);