TrkVKalVrtFitter.h

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
// TrkVKalVrtFitter.h
//
#ifndef TRKVKALVRTFITTER_VKALVRTFITTER_H
#define TRKVKALVRTFITTER_VKALVRTFITTER_H
 
#include "GaudiKernel/ToolHandle.h"
#include "AthenaBaseComps/AthAlgTool.h"
 
// Interfaces
#include  "TrkVertexFitterInterfaces/IVertexFitter.h" //base class
#include  "TrkVKalVrtFitter/ITrkVKalVrtFitter.h" //base class
#include  "TrkVKalVrtFitter/IVertexCascadeFitter.h" //base class
 
#include  "TrkNeutralParameters/NeutralParameters.h" //typedef
// MagField cache
#include "MagFieldConditions/AtlasFieldCacheCondObj.h"
#include  "xAODTracking/TrackParticleFwd.h"
#include  "xAODTracking/NeutralParticleFwd.h"
#include  "TrkVKalVrtFitter/IVKalState.h" //base class
#include  "TrkVKalVrtFitter/VKalAtlasMagFld.h" //for Trk::VKalAtlasMagFld (member)
#include  "TrkVKalVrtFitter/VKalExtPropagator.h" //for Trk::VKalExtPropagator (member)
 
#include "TrkVKalVrtCore/TrkVKalVrtCore.h"  //for VKalVrtControl (member)
//
class IChronoStatSvc;
class EventContext;
 
namespace Trk{
 
 
  enum { NTrMaxVFit=200 };
  typedef std::vector<double> dvect;
  class IExtrapolator;
  class IMagneticFieldTool;
  class Track;
  class TrackParticleBase;
 
  struct PartialMassConstraint{
    VertexID VRT;
    std::vector<int> trkInVrt;              // positions of participating tracks in common track list
    std::vector<VertexID> pseudoInVrt;      // VertexIDs of pseudos
    double Mass{};
  };
 
  struct cascadeV{                        //  general description of vertex in cascade
    VertexID vID;                         //  vertex ID - used everywhere
    std::vector<int> trkInVrt;            //  list of tracks attached to vertex directly
    VertexID outPointingV;                //  to which vertex  it points
    std::vector<VertexID> inPointingV;    //  which vertices points to it
    VertexID mergedTO;                    //  merged to another vertex (not separate anymore)
    std::vector<VertexID> mergedIN;       //  vertices attached to current
    int indexInSimpleCascade{};
    cascadeV(){ vID=-999; outPointingV=0; mergedTO=0; indexInSimpleCascade=0;};
   ~cascadeV() = default;
  };
 
 
//------------------------------------------------------------------------
  //Tool should not be used reentrantly or used publically
  class TrkVKalVrtFitter : public extends<AthAlgTool, IVertexFitter,
                                          ITrkVKalVrtFitter,
                      IVertexCascadeFitter>
  {
    friend class VKalExtPropagator;
    public:
 
        virtual StatusCode initialize() override final;
        virtual StatusCode finalize() override final;
 
        TrkVKalVrtFitter(const std::string& t, const std::string& name, const IInterface*  parent);
        virtual ~TrkVKalVrtFitter();
 
        //
        // IVertexFitter interface
        //
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>& perigeeList,
          const Amg::Vector3D& startingPoint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>& perigeeList,
          const std::vector<const NeutralParameters*>& /*neutralPerigeeList*/,
          const Amg::Vector3D& startingPoint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>& perigeeList,
          const xAOD::Vertex& constraint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>& perigeeList,
          const std::vector<const NeutralParameters*>& /*neutralPerigeeList*/,
          const xAOD::Vertex& constraint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const xAOD::TrackParticle*>& vectorTrk,
          const Amg::Vector3D& startingPoint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const xAOD::TrackParticle*>& vectorTrk,
          const xAOD::Vertex& constraint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const xAOD::TrackParticle*>& vectorTrk,
          const std::vector<const xAOD::NeutralParticle*>& vectorNeu,
          const Amg::Vector3D& startingPoint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const xAOD::TrackParticle*>& vectorTrk,
          const std::vector<const xAOD::NeutralParticle*>& vectorNeu,
          const xAOD::Vertex& constraint) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>&) const override final;
 
        virtual std::unique_ptr<xAOD::Vertex> fit(
          const EventContext& ctx,
          const std::vector<const TrackParameters*>&,
          const std::vector<const Trk::NeutralParameters*>&) const override final;
 
 
        /*--------------  Additional  xAOD  interfaces -------------*/
        std::unique_ptr<xAOD::Vertex> fit(const std::vector<const xAOD::TrackParticle*>& vectorTrk,
                           const Amg::Vector3D& constraint,
                           IVKalState& istate) const;
        std::unique_ptr<xAOD::Vertex> fit(const std::vector<const xAOD::TrackParticle*>& vectorTrk,
                           const xAOD::Vertex& constraint,
                           IVKalState& istate) const;
 
//
//  Cascade fitter interface
//
        VertexID startVertex(
          const std::vector<const xAOD::TrackParticle*>& list,
          std::span<const double> particleMass,
          IVKalState& istate,
          double massConstraint = 0.) const override final;
 
        VertexID nextVertex(const std::vector<const xAOD::TrackParticle*>& list,
                            std::span<const double> particleMass,
                            IVKalState& istate,
                            double massConstraint = 0.) const override final;
 
        VertexID nextVertex(const std::vector<const xAOD::TrackParticle*>& list,
                            std::span<const double> particleMass,
                            const std::vector<VertexID>& precedingVertices,
                            IVKalState& istate,
                            double massConstraint = 0.) const override final;
 
        VxCascadeInfo* fitCascade(IVKalState& istate,
                                  const Vertex* primVertex = 0,
                                  bool FirstDecayAtPV = false) const override final;
 
        StatusCode addMassConstraint(
          VertexID Vertex,
          const std::vector<const xAOD::TrackParticle*>& tracksInConstraint,
          const std::vector<VertexID>& verticesInConstraint,
          IVKalState& istate,
          double massConstraint) const override final;
 
        //------ specific VKalVrt staff
 
        virtual std::unique_ptr<IVKalState> makeState(
          const EventContext& ctx) const override final;
 
        virtual StatusCode VKalVrtFit(
          const std::vector<const xAOD::TrackParticle*>&,
          const std::vector<const xAOD::NeutralParticle*>&,
          Amg::Vector3D& Vertex,
          TLorentzVector& Momentum,
          long int& Charge,
          dvect& ErrorMatrix,
          dvect& Chi2PerTrk,
          std::vector<std::vector<double>>& TrkAtVrt,
          double& Chi2,
          IVKalState& istate,
          bool ifCovV0 = false) const override final;
 
        virtual StatusCode VKalVrtFit(
          const std::vector<const Perigee*>&,
          Amg::Vector3D& Vertex,
          TLorentzVector& Momentum,
          long int& Charge,
          dvect& ErrorMatrix,
          dvect& Chi2PerTrk,
          std::vector<std::vector<double>>& TrkAtVrt,
          double& Chi2,
          IVKalState& istate,
          bool ifCovV0 = false) const override final;
 
        virtual StatusCode VKalVrtFit(
          const std::vector<const TrackParameters*>&,
          const std::vector<const NeutralParameters*>&,
          Amg::Vector3D& Vertex,
          TLorentzVector& Momentum,
          long int& Charge,
          dvect& ErrorMatrix,
          dvect& Chi2PerTrk,
          std::vector<std::vector<double>>& TrkAtVrt,
          double& Chi2,
          IVKalState& istate,
          bool ifCovV0 = false) const override final;
        //------
        virtual StatusCode VKalVrtCvtTool(const Amg::Vector3D& Vertex,
                                          const TLorentzVector& Momentum,
                                          const dvect& CovVrtMom,
                                          const long int& Charge,
                                          dvect& Perigee,
                                          dvect& CovPerigee,
                                          IVKalState& istate) const override final;
        //-----
        virtual StatusCode VKalVrtFitFast(
          std::span<const xAOD::TrackParticle* const>,
          Amg::Vector3D& Vertex, double &minDZ,
          IVKalState& istate) const;
 
        virtual StatusCode VKalVrtFitFast(
          const std::span<const xAOD::TrackParticle* const>,
          Amg::Vector3D& Vertex,
          IVKalState& istate) const override final;
 
        virtual StatusCode VKalVrtFitFast(
          const std::vector<const TrackParameters*>&,
          Amg::Vector3D& Vertex,
          IVKalState& istate) const override final;
 
        virtual std::unique_ptr<Trk::Perigee>
          CreatePerigee(const std::vector<double>& VKPerigee,
                        const std::vector<double>& VKCov,
                        IVKalState& istate) const override final;
 
        virtual StatusCode VKalGetTrkWeights(
          dvect& Weights,
          const IVKalState& istate) const override final;
 
        virtual StatusCode VKalGetFullCov(long int,
                                          dvect& CovMtx,
                                          IVKalState& istate,
                                          bool = false) const override final;
 
        virtual StatusCode VKalGetMassError(
          double& Mass,
          double& MassError,
          const IVKalState& istate) const override final;
 
        virtual void setApproximateVertex(double X,
                                          double Y,
                                          double Z,
                                          IVKalState& istate) const override final;
 
        virtual void setMassForConstraint(double Mass,
                                          IVKalState& istate) const override final;
 
        virtual void setMassForConstraint(double Mass,
                                          std::span<const int>,
                                          IVKalState& istate) const override final;
 
        virtual void setRobustness(int, IVKalState& istate) const override final;
 
        virtual void setRobustScale(double, IVKalState& istate) const override final;
 
        virtual void setCnstType(int, IVKalState& istate) const override final;
 
        virtual void setVertexForConstraint(const xAOD::Vertex&,
                                            IVKalState& istate) const override final;
 
        virtual void setVertexForConstraint(double X,
                                            double Y,
                                            double Z,
                                            IVKalState& istate) const override final;
 
        virtual void setCovVrtForConstraint(double XX,
                                            double XY,
                                            double YY,
                                            double XZ,
                                            double YZ,
                                            double ZZ,
                                            IVKalState& istate) const override final;
 
        virtual void setMassInputParticles(const std::vector<double>&,
                                           IVKalState& istate) const override final;
 
        virtual double VKalGetImpact(const xAOD::TrackParticle*,
                                     const Amg::Vector3D& Vertex,
                                     const long int Charge,
                                     dvect& Impact,
                                     dvect& ImpactError,
                                     IVKalState& istate) const override final;
 
        virtual double VKalGetImpact(const Trk::Perigee*,
                                     const Amg::Vector3D& Vertex,
                                     const long int Charge,
                                     dvect& Impact,
                                     dvect& ImpactError,
                                     IVKalState& istate) const override final;
 
        virtual double VKalGetImpact(const EventContext& ctx,
                                     const xAOD::TrackParticle*,
                                     const Amg::Vector3D& Vertex,
                                     const long int Charge,
                                     dvect& Impact,
                                     dvect& ImpactError) const override final;
 
        virtual double VKalGetImpact(const EventContext& ctx,
                                     const Trk::Perigee*,
                                     const Amg::Vector3D& Vertex,
                                     const long int Charge,
                                     dvect& Impact,
                                     dvect& ImpactError) const override final;
 
        //
        // ATLAS related code
        //
      private:
        Gaudi::Property<int> m_Robustness{this, "Robustness", 0};
        Gaudi::Property<double> m_RobustScale{this, "RobustScale", 1.0};
        Gaudi::Property<double> m_cascadeCnstPrecision{this, "CascadeCnstPrecision", 1.e-4};
        Gaudi::Property<double> m_massForConstraint{this, "MassForConstraint", -1.0};
        Gaudi::Property<int> m_IterationNumber{this, "IterationNumber", 0};
        Gaudi::Property<double> m_IterationPrecision{this, "IterationPrecision", 0.0};
        Gaudi::Property<double> m_IDsizeR{this, "IDsizeR", 1150.0};
        Gaudi::Property<double> m_IDsizeZ{this, "IDsizeZ", 3000.0};
        Gaudi::Property<double> m_MSsizeR{this, "MSsizeR", 8000.0};
        Gaudi::Property<double> m_MSsizeZ{this, "MSsizeZ", 10000.0};
        Gaudi::Property<std::vector<double>> m_c_VertexForConstraint{this, "VertexForConstraint", {0,0,0}};
        Gaudi::Property<std::vector<double>> m_c_CovVrtForConstraint{this, "CovVrtForConstraint", {0,0,0,0,0,0}};
        Gaudi::Property<std::vector<double>> m_c_MassInputParticles{this, "InputParticleMasses", {}, "List of masses of input particles (pions assumed if absent)"};
 
        ToolHandle<IExtrapolator> m_extPropagator{this, "Extrapolator", "", "External propagator"};
        // Read handle for conditions object to get the field cache
        SG::ReadCondHandleKey<AtlasFieldCacheCondObj>
          m_fieldCacheCondObjInputKey{ this,
                                       "AtlasFieldCacheCondObj",
                                       "fieldCondObj",
                                       "Name of the Magnetic Field key" };
        Gaudi::Property<bool> m_firstMeasuredPoint{this, "FirstMeasuredPoint", false, "Use FirstMeasuredPoint strategy in fits"};
        Gaudi::Property<bool> m_firstMeasuredPointLimit{this, "FirstMeasuredPointLimit", false, "Use FirstMeasuredPointLimit strategy"};
    Gaudi::Property<bool> m_firstMeasuredRadiusLimit{this, "FirstMeasuredRadiusLimit", false,
                                    "Use radius of FirstMeasuredRadiusLimit as maximal vertex radius"};
        Gaudi::Property<bool> m_makeExtendedVertex{this, "MakeExtendedVertex", false, "Return VxCandidate with full covariance matrix"};
        Gaudi::Property<bool> m_useFixedField{this, "useFixedField", false, "Use fixed magnetic field instead of exact Atlas one"};
 
        bool m_isAtlasField{false};  // To allow callback and then field first call only at execute stage
 
        Gaudi::Property<bool> m_useAprioriVertex{this, "useAprioriVertexCnst", false, "Use a priori vertex constraint"};
        Gaudi::Property<bool> m_useThetaCnst{this, "useThetaCnst", false, "Use angle dTheta=0 constraint"};
        Gaudi::Property<bool> m_usePhiCnst{this, "usePhiCnst", false, "Use angle dPhi=0 constraint"};
        Gaudi::Property<bool> m_usePointingCnst{this, "usePointingCnst", false, "Use pointing to other vertex constraint"};
        Gaudi::Property<bool> m_useZPointingCnst{this, "useZPointingCnst", false, "Use ZPointing to other vertex constraint"};
        Gaudi::Property<bool> m_usePassNear{this, "usePassNearCnst", false, "Use combined particle pass near other vertex constraint"};
        Gaudi::Property<bool> m_usePassWithTrkErr{this, "usePassWithTrkErrCnst", false, "Use pass near with combined particle errors constraint"};
        Gaudi::Property<bool> m_frozenVersionForBTagging{this, "FrozenVersionForBTagging", false, "Frozen version for BTagging"};
        Gaudi::Property<bool> m_allowUltraDisplaced{this, "allowUltraDisplaced", false, "Allow ultra displaced vertices"};
        void initCnstList();
 
        //  Track material effects control
        //
        struct TrkMatControl
        {
          // Track reference point(hit) in global ATLAS frame
          Amg::Vector3D trkRefGlobPos;
          int extrapolationType;
          int TrkID;
          const TrackParameters* TrkPnt;
          double prtMass;
          Amg::Vector3D trkSavedLocalVertex; // Local VKalVrtCore vertex
        };
 
      class CascadeState
      {
      public:
        int m_cascadeSize = 0;
        std::vector<const xAOD::TrackParticle*> m_partListForCascade;
 
        std::vector<double>  m_partMassForCascade;
        std::vector<PartialMassConstraint> m_partMassCnstForCascade;
        //
        std::vector<cascadeV>    m_cascadeVList;               // list of cascade vertex objects
      };
 
      class State : public IVKalState
      {
      public:
        //
        //  Origin of global reference frame.
        //  (0,0,0) by default but can be changed by input tracks
        //
        double m_refFrameX = 0;
        double m_refFrameY = 0;
        double m_refFrameZ = 0;
        std::vector<TrkMatControl> m_trkControl;
 
        //
        // Arrays needed for fitting kernel
        //
        double m_apar[NTrMaxVFit][5]{};  // used only for fit preparation
        double m_awgt[NTrMaxVFit][15]{}; // used only for fit preparation
        long int m_ich[NTrMaxVFit]{};
        double m_parfs[NTrMaxVFit][3]{};
 
        VKalAtlasMagFld m_fitField;
        VKalVrtControl m_vkalFitControl;
        const EventContext* m_eventContext = nullptr;
        MagField::AtlasFieldCache m_fieldCache;
 
        const TrackParameters* m_globalFirstHit = nullptr;
 
        double m_save_xyzfit[3]{}; //  Save vertex after successful fit
 
        int m_FitStatus = 0; /* Fit Status flag*/
                             /* =0 - no fit. All "after fit" routines fail*/
                             /* >1 - good fit. "After fit" routines work*/
 
        //
        // Array for full error matrix
        //
        std::vector<double> m_ErrMtx;
 
        int m_planeCnstNDOF = 0; /* NDOF addition if plane constraint is used */
        std::vector<double> m_ApproximateVertex;
 
        bool m_useAprioriVertex = false;
        bool m_useThetaCnst = false;
        bool m_usePhiCnst = false;
        bool m_usePointingCnst = false;
        bool m_useZPointingCnst = false;
        bool m_usePassNear = false;
        bool m_usePassWithTrkErr = false;
        bool m_frozenVersionForBTagging = false;
        bool m_allowUltraDisplaced = false;
 
        std::vector<double> m_VertexForConstraint;
        std::vector<double> m_CovVrtForConstraint;
        double m_massForConstraint = -1;
        std::vector<double> m_partMassCnst;
        std::vector<std::vector<int>> m_partMassCnstTrk;
        int m_Robustness = 0;
        double m_RobustScale = 1;
        std::vector<double> m_MassInputParticles;
        double m_parPlaneCnst[4]{};
        double m_cnstRadius{};
        double m_cnstRadiusRef[2]{};
 
  
        std::unique_ptr<CascadeState> m_cascadeState;
 
        State()
          : m_vkalFitControl(
              VKalVrtControlBase(&m_fitField, nullptr, nullptr, nullptr, this))
        {
          m_ApproximateVertex.reserve(3);
        }
      };
 
//-----------------------------------------------------------------
//  Cascade related stuff
//
      static void makeSimpleCascade(std::vector< std::vector<int> > &, std::vector< std::vector<int> > &,
                             CascadeState& cstate) ;
      static void printSimpleCascade(std::vector< std::vector<int> > &, std::vector< std::vector<int> > &,
                              const CascadeState& cstate) ;
      static int findPositions(const std::vector<int> &,const std::vector<int> &, std::vector<int> &) ;
      static int getSimpleVIndex( const VertexID &, const CascadeState& cstate) ;
      static int indexInV( const VertexID &, const CascadeState& cstate) ;
      static int getCascadeNDoF (const CascadeState& cstate) ;
//----------------------
//  Control variables
//
 
      double m_BMAG{1.997};          /* const magnetic field  if needed */
      double m_CNVMAG{0.29979246};   /* conversion constant for MeV and MM */
 
 
      VKalExtPropagator*     m_fitPropagator{};
      const IExtrapolator*   m_InDetExtrapolator{};     
//
//
//
 
 
 
//
//  Private technical functions
//
        void setAthenaPropagator(const Trk::IExtrapolator*);
        void initState (const EventContext& ctx, State& state) const;
 
        static void FillMatrixP(AmgSymMatrix(5)& , std::vector<double>& ) ;
        static void FillMatrixP(int iTrk, AmgSymMatrix(5)& , std::vector<double>& ) ;
        static Amg::MatrixX * GiveFullMatrix(int NTrk, std::vector<double>&) ;
        bool convertAmg5SymMtx(const AmgSymMatrix(5)*, double[15] ) const;
 
        void VKalTransform(double MAG,
                           double A0V,
                           double ZV,
                           double PhiV,
                           double ThetaV,
                           double PInv,
                           const double[15],
                           long int& Charge,
                           double[5],
                           double[15]) const;
 
        std::unique_ptr<xAOD::Vertex> makeXAODVertex(int,
                                     const Amg::Vector3D&,
                                     const dvect&,
                                     const dvect&,
                                     const std::vector<dvect>&,
                                     double,
                                     State& state) const;
 
        StatusCode CvtPerigee(const std::vector<const Perigee*>& list,
                              int& ntrk,
                              State& state) const;
 
        StatusCode CvtTrackParticle(
          std::span<const xAOD::TrackParticle* const> list,
          int& ntrk,
          State& state) const;
 
        StatusCode CvtNeutralParticle(
          const std::vector<const xAOD::NeutralParticle*>& list,
          int& ntrk,
          State& state) const;
 
        StatusCode CvtTrackParameters(
          const std::vector<const TrackParameters*>& InpTrk,
          int& ntrk,
          State& state) const;
 
        StatusCode CvtNeutralParameters(
          const std::vector<const NeutralParameters*>& InpTrk,
          int& ntrk,
          State& state) const;
 
        void VKalVrtConfigureFitterCore(int NTRK, State& state) const;
 
        void VKalToTrkTrack(double curBMAG,
                            double vp1,
                            double vp2,
                            double vp3,
                            double& tp1,
                            double& tp2,
                            double& tp3) const;
 
        int VKalVrtFit3(int ntrk,
                        Amg::Vector3D& Vertex,
                        TLorentzVector& Momentum,
                        long int& Charge,
                        dvect& ErrorMatrix,
                        dvect& Chi2PerTrk,
                        std::vector<std::vector<double>>& TrkAtVrt,
                        double& Chi2,
                        State& state,
                        bool ifCovV0) const;
 
        std::unique_ptr<Perigee> CreatePerigee(double Vx,
                           double Vy,
                           double Vz,
                           const std::vector<double>& VKPerigee,
                           const std::vector<double>& VKCov,
                           State& state) const;
 
        //
        //
        static const Perigee* GetPerigee(const TrackParameters* i_ntrk) ;
 
        static int VKalGetNDOF(const State& state) ;
   };
 
} //end of namespace
 
#endif