source: git/external/TrackCovariance/VertexFit.h@ a47edcc

//
#ifndef G__VERTEXFIT_H
#define G__VERTEXFIT_H
//
#include <TMath.h>
#include <TVectorD.h>
#include <TMatrixDSym.h>
#include "ObsTrk.h"
#include <vector>
#include <iostream>
//
// Class for vertex fitting

class VertexFit {
        //
        // Vertex fitting with track parameters steering
        // Author: F. Bedeschi, INFN-Pisa, Italy
        // February 10, 2021
        //
private:
        //
        // Inputs
        Int_t fNtr;                                     // Number of tracks
        std::vector<TVectorD*> fPar;            // Input parameter array
        std::vector<TVectorD*> fParNew;         // Updated parameter array
        std::vector<TMatrixDSym*> fCov;         // Input parameter covariances
        std::vector<TMatrixDSym*> fCovNew;      // Updated parameter covariances
        // Constraints
        Bool_t fVtxCst;                         // Vertex constraint flag
        TVectorD fxCst;                         // Constraint value
        TMatrixDSym fCovCst;                    // Constraint 
        TMatrixDSym fCovCstInv;                 // Inverse of constraint covariance
        //
        // Results
        Bool_t fVtxDone;                                // Flag vertex fit completed
        Double_t fRold;                         // Current value of vertex radius
        TVectorD fXv;                           // Found vertex
        TMatrixDSym fcovXv;                     // Vertex covariance
        Double_t fChi2;                         // Vertex fit Chi2
        TVectorD fChi2List;                     // List of Chi2 contributions
        //
        // Work arrays
        std::vector<Double_t> ffi;                              // Fit phases
        std::vector<TVectorD*> fx0i;                    // Track expansion points
        std::vector<TVectorD*> fai;                             // dx/dphi
        std::vector<TVectorD*> fdi;                             // x-shift
        std::vector<Double_t> fa2i;                             // a'Wa
        std::vector<TMatrixD*> fAti;                    // A transposed
        std::vector<TMatrixDSym*> fDi;                  // W-WBW
        std::vector<TMatrixDSym*> fWi;                  // (ACA')^-1
        std::vector<TMatrixDSym*> fWinvi;               // ACA'
        //
        // Service routines
        //void InitWrkArrays();                                                 // Initializations
        void ResetWrkArrays();                                                  // Clear work arrays
        Double_t StartRadius();                                                 // Starting vertex radius determination
        Double_t FastRv(TVectorD p1, TVectorD p2);              // Fast vertex radius determination
        TMatrixDSym RegInv(TMatrixDSym& Smat0);                 // Regularized 3D matrix inversion 
        TMatrixD Fill_A(TVectorD par, Double_t phi);            // Derivative of track position wrt track parameters
        TVectorD Fill_a(TVectorD par, Double_t phi);            // Derivative of track position wrt track phase
        TVectorD Fill_x0(TVectorD par);                                 // Track position at dma to z-axis
        TVectorD Fill_x(TVectorD par, Double_t phi);            // Track position at given phase
        void UpdateTrkArrays(Int_t i);                                  // Fill track realted arrays
        void VertexFitter();                                                            // Vertex finder routine
public:
        //
        // Constructors
        VertexFit();                                                                            // Initialize waiting for tracks
        VertexFit(Int_t Ntr, ObsTrk** tracks);                  // Initialize with ObsTrk tracks
        VertexFit(Int_t Ntr, TVectorD** trkPar, TMatrixDSym** trkCov);  // Initialize with parameters and covariances
        // Destructor
        ~VertexFit();
        //
        // Accessors also trigger calculations when needed
        Int_t GetNtrk() { return fNtr; };
        TVectorD GetVtx();
        TMatrixDSym GetVtxCov();
        Double_t GetVtxChi2();
        TVectorD GetVtxChi2List();
        //
        // Handle tracks/constraints
        void AddVtxConstraint(TVectorD xv, TMatrixDSym cov);    // Add gaussian vertex constraint
        void AddTrk(TVectorD *par, TMatrixDSym *Cov);                           // Add track to input list
        void RemoveTrk(Int_t iTrk);                                                             // Remove iTrk track
        //
};

#endif