MuSAVtxFitterTool.h

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/*
Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef MUSAVTXFITTERTOOL_H
#define MUSAVTXFITTERTOOL_H
 
#include "AthenaBaseComps/AthAlgTool.h"
#include "GaudiKernel/ToolHandle.h"
#include "xAODTracking/VertexContainer.h"
#include "xAODTracking/TrackParticleContainer.h"
#include "xAODMuon/MuonContainer.h"
#include "xAODEventInfo/EventInfo.h"
#include "TrkParameters/TrackParameters.h"
#include "ITrackToVertex/ITrackToVertex.h"
#include "TrkExInterfaces/IExtrapolator.h"
#include "TrkVertexFitterInterfaces/IVertexFitter.h"
#include "TrkVKalVrtFitter/TrkVKalVrtFitter.h"
 
namespace Rec {
    static const InterfaceID IID_MuSAVtxFitterTool("MuSAVtxFitterTool", 1, 0);
 
    class MuSAVtxFitterTool:  public AthAlgTool
    {
        public:
        MuSAVtxFitterTool(const std::string& type, const std::string& name, const IInterface*  parent);
        ~MuSAVtxFitterTool();
        virtual StatusCode initialize() override;
 
        static const InterfaceID& interfaceID() { return IID_MuSAVtxFitterTool;}

 
        struct WrkVrt {
         
            bool isGood = true;                            
            std::deque<long int> selectedTrackIndices;      
            std::deque<long int> associatedTrackIndices;    
            std::vector<std::shared_ptr<const xAOD::TrackParticle>> newExtrapolatedTracks; 
            std::vector<const xAOD::Muon*> muonCandidates;  
            Amg::Vector3D        pos;                    
            TLorentzVector       mom;                 
            std::vector<double>  cov;                 
            double               chi2 = 0;                  
            double               chi2Core = 0;             
            std::vector<double>  chi2PerTrk;                
            long int             charge = 0;                
            std::vector< std::vector<double> > trkAtVrt;    
            double               minOpAng = 0;            
            int                  closestWrkVrtIndex = 0;    
            double               closestWrkVrtValue = 0;    
 
            inline double ndof() const { return 2.0*( selectedTrackIndices.size() + associatedTrackIndices.size() ) - 3.0; } //currently always 1, because only 2trk fit, but left for future developments.
            inline double ndofCore() const { return 2.0*( selectedTrackIndices.size() ) - 3.0; } //currently always 1, because only 2trk fit, but left for future developments. Uses only seeding MSTPs ("core")
            inline unsigned nTracksTotal() const { return selectedTrackIndices.size() + associatedTrackIndices.size(); } 
            inline double fitQuality() const { return chi2 / ndof(); }
    };
 
        // takes in MSTPs from SA muons and extrapolates them backwards without any constraint, producing a new xAOD::TrackParticle for input to the vertex fitter
        std::unique_ptr<xAOD::TrackParticle> extrapolateMuSA(const xAOD::TrackParticle& trk, const xAOD::EventInfo& eventInfo, const EventContext& ctx) const;
 
        // performs the MuSA vertex fit routine using the VKalVrtFitter tool
        StatusCode doMuSAVtxFit(std::vector<MuSAVtxFitterTool::WrkVrt>& workVerticesContainer, const xAOD::MuonContainer& muonContainer, const xAOD::EventInfo& eventInfo, const EventContext& ctx) const;
 
        // does post-fit selections on vertices in the workVerticesContainer
        StatusCode doPostFitSelections(std::vector<MuSAVtxFitterTool::WrkVrt>& workVerticesContainer) const;
 
        // selects the best remaining vertices from the workVerticesContainer and resolves ambiguities to produce unique track-to-vertex associations
        StatusCode selectBestVertices(std::vector<MuSAVtxFitterTool::WrkVrt>& workVerticesContainer) const;
        
        private:
 
        ToolHandle<Trk::ITrkVKalVrtFitter> m_vertexFitter{
            this, "VertexFitterTool", "Trk::TrkVKalVrtFitter", "Vertex fitter tool"};
        ToolHandle <Trk::IExtrapolator> m_extrapolator{
            this,"Extrapolator","Trk::Extrapolator/AtlasExtrapolator","ATLAS Extrapolator tool"};
        
        DoubleProperty m_etaCutMSTP{this, "etaCutMSTP", 2.5, "Maximum |eta| of input MSTPs"};
        DoubleProperty m_baseChi2Cut{this, "baseChi2Cut", 50., "Maximum allowed chi2 of saved vertices"};
        Gaudi::Property<bool> m_doValidation{this, "doValidation", false, "Vertex every MSTP in input as part of validation process"};
 
    };
}
 
#endif