| 1 | /*
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| 2 | Example of using vertex fitter class to fit primary vertex
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| 3 | assumed to be generated in (0,0,0).
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| 4 | To run compiled version:
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| 5 | root
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| 6 | root> .L examples/LoadPvtxFit.C+
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| 7 | root> LoadPVtxFit()
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| 8 | root> ExamplePVtxFit("infile.root", Nevents)
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| 9 |
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| 10 | March 4, 2021
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| 11 | F. Bedeschi, INFN-Pisa, Italy
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| 12 | */
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| 13 |
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| 14 | #include "classes/DelphesClasses.h"
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| 15 | #include "external/ExRootAnalysis/ExRootTreeReader.h"
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| 16 | #include "modules/TrackCovariance.h"
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| 17 | #include "external/TrackCovariance/TrkUtil.h"
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| 18 | #include "external/TrackCovariance/VertexFit.h"
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| 19 |
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| 20 | #include <TClonesArray.h>
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| 21 | #include <TChain.h>
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| 22 | #include <TVectorD.h>
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| 23 | #include <TMatrixDSym.h>
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| 24 | #include <TH1.h>
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| 25 | #include <TCanvas.h>
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| 26 | #include <TStyle.h>
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| 27 |
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| 28 | //------------------------------------------------------------------------------
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| 29 |
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| 30 | void ExamplePVtxFit(const char* inputFile, Int_t Nevent = 5)
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| 31 | {
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| 32 | // Create chain of root trees
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| 33 | TChain chain("Delphes");
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| 34 | chain.Add(inputFile);
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| 35 |
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| 36 | // Create object of class ExRootTreeReader
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| 37 | ExRootTreeReader* treeReader = new ExRootTreeReader(&chain);
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| 38 | Long64_t numberOfEntries = treeReader->GetEntries();
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| 39 |
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| 40 | // Get pointers to branches used in this analysis
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| 41 | TClonesArray* branchGenPart = treeReader->UseBranch("Particle");
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| 42 | TClonesArray* branchTrack = treeReader->UseBranch("Track");
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| 43 |
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| 44 | // Book histograms
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| 45 | Int_t Nbin = 100;
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| 46 | TH1D* hXpull = new TH1D("hXpull", "Pull X vertex component", Nbin, -10., 10.);
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| 47 | TH1D* hYpull = new TH1D("hYpull", "Pull Y vertex component", Nbin, -10., 10.);
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| 48 | TH1D* hZpull = new TH1D("hZpull", "Pull Z vertex component", Nbin, -10., 10.);
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| 49 | TH1D* hChi2 = new TH1D("hChi2", "Vertex #chi^{2}/N_{dof}", Nbin, 0., 10.);
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| 50 | //
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| 51 | // Loop over all events
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| 52 | Int_t Nev = TMath::Min(Nevent, (Int_t) numberOfEntries);
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| 53 | for (Int_t entry = 0; entry < Nev; ++entry)
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| 54 | {
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| 55 | // Load selected branches with data from specified event
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| 56 | treeReader->ReadEntry(entry);
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| 57 | Int_t Ntr = 0; // # of tracks from primary vertex
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| 58 | Int_t NtrG = branchTrack->GetEntries(); // Total # of tracks
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| 59 | TVectorD** pr = new TVectorD * [NtrG];
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| 60 | TMatrixDSym** cv = new TMatrixDSym * [NtrG];
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| 61 | // If event contains at least 1 track
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| 62 | //
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| 63 | if (branchTrack->GetEntries() > 0)
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| 64 | {
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| 65 | // Loop on tracks
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| 66 | for (Int_t it = 0; it < branchTrack->GetEntries(); it++)
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| 67 | {
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| 68 | Track* trk = (Track*)branchTrack->At(it);
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| 69 | //
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| 70 | // Get associated generated particle
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| 71 | GenParticle* gp = (GenParticle*)trk->Particle.GetObject();
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| 72 | //
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| 73 | // Position of origin (mm)
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| 74 | Double_t x = gp->X;
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| 75 | Double_t y = gp->Y;
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| 76 | Double_t z = gp->Z;
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| 77 | //
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| 78 | // Select group of tracks originating from the primary vertex
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| 79 | if (x == 0.0 && y == 0.0)
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| 80 | {
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| 81 | //
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| 82 | // Reconstructed track parameters
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| 83 | Double_t obsD0 = trk->D0;
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| 84 | Double_t obsPhi = trk->Phi;
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| 85 | Double_t obsC = trk->C;
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| 86 | Double_t obsZ0 = trk->DZ;
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| 87 | Double_t obsCtg = trk->CtgTheta;
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| 88 | Double_t oPar[5] = { obsD0, obsPhi, obsC, obsZ0, obsCtg };
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| 89 | TVectorD obsPar(5, oPar); // Fill observed parameters
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| 90 | //
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| 91 | pr[Ntr] = new TVectorD(obsPar);
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| 92 | cv[Ntr] = new TMatrixDSym(TrkUtil::CovToMm(trk->CovarianceMatrix()));
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| 93 | Ntr++;
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| 94 | }
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| 95 | } // End loop on tracks
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| 96 | }
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| 97 | //
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| 98 | // Fit primary vertex
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| 99 | Int_t MinTrk = 2; // Minumum # tracks for vertex fit
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| 100 | if (Ntr >= MinTrk) {
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| 101 | VertexFit* Vtx = new VertexFit(Ntr, pr, cv);
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| 102 | TVectorD xvtx = Vtx->GetVtx();
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| 103 | TMatrixDSym covX = Vtx->GetVtxCov();
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| 104 | Double_t Chi2 = Vtx->GetVtxChi2();
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| 105 | Double_t Ndof = 2 * (Double_t)Ntr - 3;
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| 106 | Double_t PullX = xvtx(0) / TMath::Sqrt(covX(0, 0));
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| 107 | Double_t PullY = xvtx(1) / TMath::Sqrt(covX(1, 1));
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| 108 | Double_t PullZ = xvtx(2) / TMath::Sqrt(covX(2, 2));
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| 109 | //
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| 110 | // Fill histograms
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| 111 | hXpull->Fill(PullX);
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| 112 | hYpull->Fill(PullY);
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| 113 | hZpull->Fill(PullZ);
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| 114 | hChi2->Fill(Chi2 / Ndof);
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| 115 | }
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| 116 |
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| 117 | //
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| 118 | // Cleanup
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| 119 | for (Int_t i = 0; i < Ntr; i++) delete pr[i];
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| 120 | for (Int_t i = 0; i < Ntr; i++) delete cv[i];
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| 121 | delete[] pr;
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| 122 | delete[] cv;
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| 123 | }
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| 124 | //
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| 125 | // Show resulting histograms
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| 126 | //
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| 127 | TCanvas* Cnv = new TCanvas("Cnv", "Delphes generated track plots", 50, 50, 900, 500);
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| 128 | Cnv->Divide(2, 2);
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| 129 | Cnv->cd(1); gPad->SetLogy(1); gStyle->SetOptFit(1111);
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| 130 | hXpull->Fit("gaus"); hXpull->Draw();
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| 131 | Cnv->cd(2); gPad->SetLogy(1); gStyle->SetOptFit(1111);
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| 132 | hYpull->Fit("gaus"); hYpull->Draw();
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| 133 | Cnv->cd(3); gPad->SetLogy(1); gStyle->SetOptFit(1111);
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| 134 | hZpull->Fit("gaus"); hZpull->Draw();
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| 135 | Cnv->cd(4); hChi2->Draw();
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| 136 | }
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