void propagate(TLorentzVector &l, TVector3 &p, float charge, TH2F* hpro=0)
{
  double x0=p.X()/100;
  double y0=p.Y()/100;
  double z0=p.Z()/100;
  
  double px0=l.Px();
  double py0=l.Py();
  double pz0=l.Pz();
  
  double B=2;
  
  double pt=sqrt(px0*px0+py0*py0);
  double lambda=pz0/pt;
  double s_t=z0/lambda;
  double a=-0.2998*B*charge/3;
  double rho=a/pt;
  
  //cout <<hpro<<endl;
  
  if (hpro) 
  {
    int steps=100;
    double dz=z0/steps;
    for (int i=0;i<steps;i++)
    {
      if (i==90) i=99;
      double s_tt=(i+1)*dz/lambda;
      double cosrst=cos(rho*s_tt);
      double sinrst=sin(rho*s_tt);
  
      double px = px0*cosrst + py0*sinrst;
      double py = py0*cosrst - px0*sinrst;
      //double pz = pz0;
  
      double xt=x0 - px/a*sinrst + py/a*(1-cosrst); 
      double yt=y0 - py/a*sinrst - px/a*(1-cosrst); 
      //double z=z0 - lambda*s_tt;
      
       hpro->Fill(xt,yt);
    }
  }
  
  //cout <<"lam="<<atan(1/lambda)/3.1416*180<<" "<<rho<<" "<<s_t<<endl;
  
  double cosrs=cos(rho*s_t);
  double sinrs=sin(rho*s_t);
  
  double px = px0*cosrs + py0*sinrs;
  double py = py0*cosrs - px0*sinrs;
  double pz = pz0;
  
  double x=x0 - px/a*sinrs + py/a*(1-cosrs); 
  double y=y0 - py/a*sinrs - px/a*(1-cosrs); 
  double z=z0 - lambda*s_t;
  
  l.SetX(px);
  l.SetY(py);
  l.SetZ(pz);
  
  p.SetX(x*100);
  p.SetY(y*100);
  p.SetZ(z*100);
}

void ana_Lambda(TString fname="tmp.root",int num=0)
{
    TStopwatch timer;
    timer.Start();
    
    gROOT->LoadMacro("$VMCWORKDIR/gconfig/basiclibs.C");
    basiclibs();
    
    // **** the library is needed in order to use the TCandidate and TCandList etc
    gSystem->Load("libRho");
    
    TCanvas *c1=new TCanvas("c1","c1",600,600);
    
    // **** access the datastructure holding the particle lists
    //
    TFile* f = new TFile(fname.Data());
    TTree *t=f->Get("cbmsim") ;
    
    // **** for every event, a TCLonesArray with the candidates is stored in cbmsim
    //
    TClonesArray *fChrgCands=new TClonesArray("TCandidate");
    //TClonesArray *fNeutCands=new TClonesArray("TCandidate");
    //TClonesArray *fMcCands=new TClonesArray("TCandidate");
    
    t->SetBranchAddress("PndChargedCandidates",&fChrgCands);
    //t->SetBranchAddress("PndNeutralCandidates",&fNeutCands);
    //t->SetBranchAddress("PndMcTracks",&fMcCands);
    
    TCandidate *tc;
    
    // **** create and setup some histos for QA plots
    //
    TH1F *ppimass = new TH1F("ppimass","p pi cands",100,1.115-0.2,1.115+0.2);
    
    ppimass->SetMinimum(0);
    
    if (num==0) num= t->GetEntriesFast();
    cout <<"\n####### Processing "<<num <<" events...\n"<<endl;
    
    // **** create all the particle lists we'll need for rebuilding the decay tree
    //
    TCandList mcCands;
    
    TCandList allCands,chargedCands, minusCands, plusCands, pplusCands, pminusCands, piplusCands, piminusCands;
    
    TCandList ppiCands;
    
    // **** create and configure the selectors/filters we'd like to use later
    //
    TPidChargedSelector *chargedSel = new TPidChargedSelector;
    TPidNeutralSelector *neutralSel = new TPidNeutralSelector;
    
    TPidPlusSelector    *plusSel    = new TPidPlusSelector;
    TPidMinusSelector   *minusSel   = new TPidMinusSelector;
    
    // **** mass selectors for the resonances/composites
    //
    TPidSimplePionSelector *piSel    = new TPidSimplePionSelector();
    piSel->SetCriterion("veryLoose");
    TPidSimpleProtonSelector *pSel    = new TPidSimpleProtonSelector();
    pSel->SetCriterion("veryLoose");
    
    int i1,i2;
    
    // **** loop over all _events_
    //
    for (Int_t j=0; j< num;j++)
    {
       if ((j%100)==0) cout <<"evt "<<j<<endl;

	t->GetEntry(j);
	TFactory::Instance()->Reset();
	
	chargedCands.Cleanup();
	
	// **** loop over all Candidates and add them to the list allCands
	//    
	
	for (i1=0; i1<fChrgCands->GetEntriesFast(); i1++){
	    tc = (TCandidate *)fChrgCands->At(i1);
	    
	    TLorentzVector l=tc->P4();
	    TVector3 p=tc->Pos();
	    
	    propagate(l,p,tc->GetCharge());
	    tc->SetP4(l);
	    tc->SetPos(p);
	    
	    chargedCands.Add(*tc);
	    
	}
	
	plusCands.Select(chargedCands, plusSel);
	minusCands.Select(chargedCands, minusSel);
	
	pplusCands.Select(plusCands,pSel);
	pminusCands.Select(minusCands,pSel);
	
	piplusCands.Select(plusCands,piSel);
	piminusCands.Select(minusCands,piSel);
	
	cout <<"chrg:"<<chargedCands.GetLength()<<" ";
	cout <<"plus:"<<plusCands.GetLength()<<" ";
	cout <<"minus:"<<minusCands.GetLength()<<" ";
	cout <<"p+:"<<pplusCands.GetLength()<<" ";
	cout <<"p-:"<<pminusCands.GetLength()<<" ";
	cout <<"pi+:"<<piplusCands.GetLength()<<" ";
	cout <<"pi-:"<<piminusCands.GetLength()<<endl;
	
	// **** select all the basic list
	//
	
	//cout <<"c:"<<chargedCands.GetLength()<<" n:"<<neutralCands.GetLength()<<endl;
	
	
	ppiCands.Combine(pplusCands,piminusCands);
	ppiCands.CombineAndAppend(pminusCands,piplusCands);
	
	TCandListIterator iterP(ppiCands);
	while (tc=iterP.Next()) ppimass->Fill(tc->M()); 
    }
    // **** plot all that stuff
    //
    c1->cd(1);
    ppimass->Draw();
    
    
    timer.Stop();
    Double_t rtime = timer.RealTime();
    Double_t ctime = timer.CpuTime();
    
    printf("RealTime=%f seconds, CpuTime=%f seconds\n",rtime,ctime);
    
}

/*void printTree(TCandidate *tc, int level=0)
{
  int i=0;
  int nd=tc->NDaughters();
  if (nd==0) return;
  cout <<tc->Uid()<<"("<<level<<") -> ";
  for (i=0;i<nd;i++) cout<<tc->Daughter(i)->Uid()<<"  ";
  cout <<endl;
  for (i=0;i<nd;i++) printTree(tc->Daughter(i),level+1);
  if (level==0) cout <<endl;
}
*/