thailand2017/tut_ana_fit.C

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class RhoCandList;
class RhoCandidate;
class PndAnaPidSelector;
class PndAnaPidCombiner;
class PndAnalysis;

// **** some auxilliary functions in auxtut.C ****
// - FairRunAna* initrun(TString prefix, TString outfile, int min=-1, int max=-1) --> Init FairRunAna
// - plotmyhistos()               --> Plots all histograms in current TDirectory on a autosized canvas
// - writemyhistos()              --> Writes all histos in current TFile 
// - fillM(RhoCandList l, TH1* h) --> Fill mass histogram h with masses of candidates in l
// - RemoveGeoManager()           --> Temporary fix for error on macro exit   
// **** some auxilliary functions in auxtut.C ****
#include "auxtut.C"

void tut_ana_fit(int nevts = 0, TString prefix = "signal")
{
        // *** some variables
        int i=0,j=0, k=0, l=0;
        gStyle->SetOptFit(1011);
        
        // *** Initialize FairRunAna with defaults      
        TString OutFile="out_dummy.root";  
        FairRunAna* fRun = initrun(prefix, OutFile);
        fRun->Init();
        
        // *** create an output file for all histograms
        TFile *out = TFile::Open(prefix+"_ana_fit.root","RECREATE");
        
        // #### EXERCISE:  create some histograms
        TH1F *hjpsim_all     = new TH1F("hjpsim_all","J/#psi mass",200,0,4.5);
        TH1F *hjpsim_vf      = new TH1F("hjpsim_vf", "J/#psi mass (vertex fit)",200,0,4.5);     
        TH1F *hjpsi_chi2_vf  = new TH1F("hjpsi_chi2_vf", "J/#psi: #chi^{2} vertex fit",100,0,10);
        TH1F *hjpsi_prob_vf  = new TH1F("hjpsi_prob_vf", "J/#psi: Prob vertex fit",100,0,1);
        // ....
        
        // ------------------------------
        // Now the analysis stuff comes...
        // ------------------------------
        
        
        // *** the data reader object
        PndAnalysis* theAnalysis = new PndAnalysis();
        if (nevts==0) nevts= theAnalysis->GetEntries();
        
        // *** RhoCandLists for the analysis
        RhoCandList muplus, muminus, piplus, piminus, jpsi, pbarp;
        
        // *** Mass selector for the jpsi cands
        double m0_jpsi = TDatabasePDG::Instance()->GetParticle("J/psi")->Mass();   // Get nominal PDG mass of the J/psi
        RhoMassParticleSelector *jpsiMassSel=new RhoMassParticleSelector("jpsi",m0_jpsi,1.0);
        
        // *** the lorentz vector of the initial pbarp, needed by 4C fitter
        TLorentzVector ini(0, 0, 6.231552, 7.240065);
        
        // ***
        // the event loop
        // ***
        while (theAnalysis->GetEvent() && i++<nevts)
        {
                if ((i%100)==0) cout<<"evt " << i << endl;
                                
                // *** Select with no PID info ('All'); type and mass are set           
                theAnalysis->FillList(muplus,  "MuonAllPlus");
                theAnalysis->FillList(muminus, "MuonAllMinus");
                theAnalysis->FillList(piplus,  "PionAllPlus");
                theAnalysis->FillList(piminus, "PionAllMinus");
                
                // *** combinatorics for J/psi -> mu+ mu-
                jpsi.Combine(muplus, muminus);
                
                // ***
                // *** do VERTEX FIT (J/psi)
                // ***
                for (j=0;j<jpsi.GetLength();++j) 
                {
                        // #### EXERCISE:  fill unfitted mass in histogram
                        // ... ->Fill(...
                        
                        RhoKinVtxFitter vtxfitter(jpsi[j]);     // instantiate a vertex fitter
                        vtxfitter.Fit();
                        
                        double chi2_vtx = vtxfitter.GetChi2();  // access chi2 of fit
                        double prob_vtx = vtxfitter.GetProb();  // access probability of fit
                        
                        // #### EXERCISE:  fill chi2 and prob in histogram              
                        // hjpsi_chi2_vf->Fill(...
                        // ...
                                                
                        if ( prob_vtx > 0.01 )                          // when good enough, fill some histos
                        {
                                RhoCandidate *jfit = jpsi[j]->GetFit(); // access the fitted cand
                                TVector3 jVtx=jfit->Pos();                              // and the decay vertex position
                                
                                // #### EXERCISE:  fill fitted mass and vertex position in histograms   
                                // ...
                        }
                }
                
                // *** some rough mass selection
                jpsi.Select(jpsiMassSel);
                
                // *** combinatorics for pbarp -> J/psi pi+ pi-
                pbarp.Combine(jpsi, piplus, piminus);
                
                // ***
                // *** do 4C FIT (initial psi(2S) system)
                // ***
                for (j=0;j<pbarp.GetLength();++j) 
                {
                        // #### EXERCISE:  fill unfitted mass in histogram
                        // ... ->Fill(...
                        
                        RhoKinFitter fitter(pbarp[j]);  // instantiate the kin fitter in psi(2S)
                        fitter.Add4MomConstraint(ini);  // set 4 constraint
                        fitter.Fit();                   // do fit
                        
                        double chi2_4c = fitter.GetChi2();      // get chi2 of fit
                        double prob_4c = fitter.GetProb();      // access probability of fit
                        
                        // #### EXERCISE:  fill chi2 and prob in histogram              
                        // hpbarp_chi2_vf->Fill(...
                        // ...
                        
                        if ( prob_4c > 0.01 )            // when good enough, fill some histo
                        {
                                RhoCandidate *jfit = pbarp[j]->Daughter(0)->GetFit();   // get fitted J/psi

                                // #### EXERCISE:  fill fitted mass and vertex position in histograms   
                                // ...
                        }
                }               
                
                // ***
                // *** do MASS CONSTRAINT FIT (J/psi)
                // ***
                for (j=0;j<jpsi.GetLength();++j) 
                {
                        RhoKinFitter mfitter(jpsi[j]);      // instantiate the RhoKinFitter in psi(2S)
                        mfitter.AddMassConstraint(m0_jpsi); // add the mass constraint
                        mfitter.Fit();                      // do fit
                        
                        // #### EXERCISE:  fill chi2 and prob in histogram
                        // double chi2_m = ...
                        // hpbarp_chi2_vf->Fill(...
                        
                        // #### EXERCISE:  cut on prob and fill surviving candidates mass in histogram
                        // if (....
                }               
                
        }
        
        // *** change to directory where histograms are created
        out->cd();

        // *** plot all histos
        plotmyhistos();
        
        // *** write out all the histos to file
        int nhist = writemyhistos();
        cout<<"Writing "<<nhist<<" histograms to file"<<endl;           
        out->Save();    
        
        // *** temporaty fix to avoid error on macro exit
        RemoveGeoManager();
}