edm4eic.yaml

# SPDX-License-Identifier: LGPL-3.0-or-later
# Copyright (C) 2023 Sylvester Joosten, Whitney Armstrong, Wouter Deconinck, Christopher Dilks
# Some datatypes based on EDM4hep. EDM4hep license applies to those sections.
---
## Schema versioning
## This is required to be an integer, and defined as 100*major+minor.
## Patch level changes are required to be schema invariant.
##
## If there are schema version changes that can be evolved, see the podio documentation
## for an example: https://github.com/hegner/podio/blob/master/tests/schema_evolution.yaml
##
schema_version: 800

options :
  # should getters / setters be prefixed with get / set?
  getSyntax: True
  # should POD members be exposed with getters/setters in classes that have them as members?
  exposePODMembers: False
  includeSubfolder: True

## Some guidance:
##  - Ensure data products usable without library dependencies (favor PODness where
##    possible).
##  - Move towards EDM4hep compatibility (to allow a transition to mainly use EDM4hep).
##        - migrate away from custom indices in favor of podio relations
##  - Use float most of the time except for 4-vectors where ppm precision is important.
##  - Data alignment: 
##        - data should be aligned with a 64-bit structure where possible.
##        - when using 32 bit values, use them in pairs (or after all 64-bit variables are defined). 
##        - same goes for 16-bit values (keep them aligned with the largest following component)
##  - Explicitly specify the integer length (use the typedefs from <cstdint>, 
##    such as int32_t etc)

components:

  edm4eic::CovDiag3f:
    Members:
      - float xx
      - float yy
      - float zz
    ExtraCode:
      declaration: "
        CovDiag3f() : xx{0}, yy{0}, zz{0} {}\n
        CovDiag3f(double x, double y, double z)\n
          : xx{static_cast<float>(x)}, yy{static_cast<float>(y)}, zz{static_cast<float>(z)} {}\n
        float operator()(unsigned i, unsigned j) const {return (i == j) ? *(&xx + i) : 0.;}\n
        "

  edm4eic::Cov2f:
    Members:
      - float xx
      - float yy
      - float xy
    ExtraCode:
      declaration: "
        Cov2f() : xx{0}, yy{0}, xy{0} {}\n
        Cov2f(double vx, double vy, double vxy = 0)\n
          : xx{static_cast<float>(vx)}, yy{static_cast<float>(vy)}, xy{static_cast<float>(vxy)} {}\n
        float operator()(unsigned i, unsigned j) const {\n
          // diagonal\n
          if (i == j) {\n
            return *(&xx + i);\n
          }\n
          // off-diagonal\n
          // we have as options (0, 1), and (1, 0)\n
          // note that, starting from xy, we find the correct element at (i+j+1)/2)\n
          return *(&xy + (i + j + 1) / 2);\n
        }\n
      "

  edm4eic::Cov3f:
    Members:
      - float xx
      - float yy
      - float zz
      - float xy
      - float xz
      - float yz
    ExtraCode:
      declaration: "
        Cov3f() : xx{0}, yy{0}, zz{0}, xy{0}, xz{0}, yz{0} {}\n
        Cov3f(double vx, double vy, double vz, double vxy = 0, double vxz = 0, double vyz = 0)\n
          : xx{static_cast<float>(vx)}, yy{static_cast<float>(vy)}, zz{static_cast<float>(vz)},\n
            xy{static_cast<float>(vxy)}, xz{static_cast<float>(vxz)}, yz{static_cast<float>(vyz)} {}\n
        float operator()(unsigned i, unsigned j) const {\n
          // diagonal\n
          if (i == j) {\n
            return *(&xx + i);\n
          }\n
          // off-diagonal\n
          // we have as options (0, 1), (0, 2) and (1, 2) (and mirrored)\n
          // note that, starting from xy, we find the correct element at (i+j-1)\n
          return *(&xy + i + j - 1);\n
        }\n
      "

  edm4eic::Cov4f:
    Members:
      - float xx 
      - float yy
      - float zz
      - float tt
      - float xy
      - float xz
      - float xt
      - float yz
      - float yt
      - float zt
    ExtraCode:
      declaration: "
        Cov4f() : xx{0}, yy{0}, zz{0}, tt{0}, xy{0}, xz{0}, xt{0}, yz{0}, yt{0}, zt{0} {}\n
        Cov4f(double vx, double vy, double vz, double vt,\n
              double vxy = 0, double vxz = 0, double vxt = 0,\n
              double vyz = 0, double vyt = 0, double vzt = 0)\n
          : xx{static_cast<float>(vx)}, yy{static_cast<float>(vy)}, zz{static_cast<float>(vz)}, tt{static_cast<float>(vt)},\n
            xy{static_cast<float>(vxy)}, xz{static_cast<float>(vxz)}, xt{static_cast<float>(vxt)},\n
            yz{static_cast<float>(vyz)}, yt{static_cast<float>(vyt)}, zt{static_cast<float>(vzt)} {}\n
        float operator()(unsigned i, unsigned j) const {\n
          // diagonal\n
          if (i == j) {\n
            return *(&xx + i);\n
          // off-diagonal, can probably be done with less if statements \n
          } else {\n
            if (i > j) { \n
              std::swap(i,j); \n
            } \n
            if (i == 0) { \n
              return *(&xy + j - 1); \n
            } else if (i == 1) { \n
              return *(&yz + j - 2); \n
            } else { \n
              return zt; \n
            } \n
          } \n
        }\n
      "

  edm4eic::Cov6f:
    Members:
      - std::array<float, 21> covariance  // 6d triangular packed covariance matrix
    ExtraCode:
      declaration: "
        Cov6f() : covariance{} {}\n
        Cov6f(std::array<float, 21> vcov) : covariance{vcov}{}\n
        float operator()(unsigned i, unsigned j) const {\n
          if(i > j) {\n
            std::swap(i, j);\n
            }\n
          return covariance[i + 1 + (j + 1) * (j) / 2 - 1];\n
        }\n
        float& operator()(unsigned i, unsigned j) {\n
          if(i > j) {\n
            std::swap(i, j);\n
            }\n
          return covariance[i + 1 + (j + 1) * (j) / 2 - 1];\n
        }\n
      "

  ## A point along a track
  edm4eic::TrackPoint:
    Members:
      - uint64_t          surface         // Surface track was propagated to (possibly multiple per detector)
      - uint32_t          system          // Detector system track was propagated to
      - edm4hep::Vector3f position        // Position of the trajectory point [mm]
      - edm4eic::Cov3f    positionError   // Error on the position
      - edm4hep::Vector3f momentum        // 3-momentum at the point [GeV]
      - edm4eic::Cov3f    momentumError   // Error on the 3-momentum
      - float             time            // Time at this point [ns]
      - float             timeError       // Error on the time at this point
      - float             theta           // polar direction of the track at the surface [rad]
      - float             phi             // azimuthal direction of the track at the surface [rad]
      - edm4eic::Cov2f    directionError  // Error on the polar and azimuthal angles
      - float             pathlength      // Pathlength from the origin to this point
      - float             pathlengthError // Error on the pathlength

  ## PID hypothesis from Cherenkov detectors
  edm4eic::CherenkovParticleIDHypothesis:
    Members:
      - int32_t           PDG             // PDG code
      - float             npe             // Overall photoelectron count
      - float             weight          // Weight of this hypothesis, such as likelihood, moment, etc.

  ## Representation of surfaces, including dynamic perigee surfaces (identical to ActsPodioEdm::Surface)
  edm4eic::Surface:
    Members: 
      - int surfaceType                   // Cone = 0, Cylinder = 1, Disc = 2, Perigee = 3, Plane = 4, Straw = 5, Curvilinear = 6, Other = 7
      - int boundsType                    // eCone = 0, eCylinder = 1, eDiamond = 2, eDisc = 3, eEllipse = 4, eLine = 5, eRectangle = 6, eTrapezoid = 7, eTriangle = 8, eDiscTrapezoid = 9, eConvexPolygon = 10, eAnnulus = 11, eBoundless = 12, eOther = 13
      - uint64_t geometryId               // bit pattern volume:8,boundary:8,layer:12,approach:8,sensitive:20,extra:8
      - uint64_t identifier               // identifier of associated detector element, if available
      - std::array<double,10> boundValues // bound values, e.g. for RectangleBounds, BoundValues are eMinX = 0, eMinY = 1, eMaxX = 2, eMaxY = 3, eSize = 4
      - uint32_t boundValuesSize          // size of bound values
      - std::array<double,16> transform   // row-wise 4x4 affine transform [R T; 0 1] with 3x3 rotation matrix R and translation column 3-vector T

datatypes:

  edm4eic::Tensor:
    Description: "Tensor type for use in training in inference of ML models"
    Author: "D. Kalinkin"
    Members:
      - int32_t           elementType     // Data type in the same encoding as "ONNXTensorElementDataType", 1 - float, 7 - int64
    VectorMembers:
      - int64_t           shape           // Vector of tensor lengths along its axes
      - float             floatData       // Iff elementType==1, values are stored here
      - int64_t           int64Data       // Iff elementType==7, values are stored here

  ## ==========================================================================
  ## Particle info
  ## ==========================================================================

  edm4eic::ReconstructedParticle:
    Description: "EIC Reconstructed Particle"
    Author: "W. Armstrong, S. Joosten, F. Gaede"
    Members:
      - int32_t           type              // type of reconstructed particle. Check/set collection parameters ReconstructedParticleTypeNames and ReconstructedParticleTypeValues.
      - float             energy            // [GeV] energy of the reconstructed particle. Four momentum state is not kept consistent internally.
      - edm4hep::Vector3f momentum          // [GeV] particle momentum. Four momentum state is not kept consistent internally.
      - edm4hep::Vector3f referencePoint    // [mm] reference, i.e. where the particle has been measured
      - float             charge            // charge of the reconstructed particle.
      - float             mass              // [GeV] mass of the reconstructed particle, set independently from four vector. Four momentum state is not kept consistent internally.
      - float             goodnessOfPID     // overall goodness of the PID on a scale of [0;1]
      - edm4eic::Cov4f    covMatrix         // covariance matrix of the reconstructed particle 4vector (10 parameters).
      ##@TODO: deviation from EDM4hep: store explicit PDG ID here. Needs to be discussed how we
      ##       move forward as this could easiliy become unwieldy without this information here.
      ##       The only acceptable alternative would be to store reconstructed identified 
      ##       particles in separate collections for the different particle types (which would
      ##       require some algorithmic changes but might work. Doing both might even make
      ##       sense. Needs some discussion, note that PID is more emphasized in NP than
      ##       HEP).
      - int32_t           PDG               // PDG code for this particle
      ## @TODO: Do we need timing info? Or do we rely on the start vertex time?
    OneToOneRelations:
      - edm4eic::Vertex      startVertex    // Start vertex associated to this particle
      - edm4hep::ParticleID  particleIDUsed // particle ID used for the kinematics of this particle
    OneToManyRelations:
      - edm4eic::Cluster     clusters       // Clusters used for this particle
      - edm4eic::Track       tracks         // Tracks used for this particle
      - edm4eic::ReconstructedParticle particles // Reconstructed particles that have been combined to this particle
      - edm4hep::ParticleID  particleIDs    // All associated particle IDs for this particle (not sorted by likelihood)
    ExtraCode:
      declaration: "
        bool isCompound() const {return particles_size() > 0;}\n
        "

  ## ==========================================================================
  ## Calorimetry
  ## ==========================================================================
  edm4eic::CalorimeterHit:
    Description: "Calorimeter hit"
    Author: "W. Armstrong, S. Joosten"
    Members:
      - uint64_t          cellID            // The detector specific (geometrical) cell id.
      - float             energy            // The energy for this hit in [GeV].
      - float             energyError       // Error on energy [GeV].
      - float             time              // The time of the hit in [ns].
      - float             timeError         // Error on the time
      - edm4hep::Vector3f position          // The global position of the hit in world coordinates [mm].
      - edm4hep::Vector3f dimension         // The dimension information of the cell [mm].
      - int32_t           sector            // Sector that this hit occurred in
      - int32_t           layer             // Layer that the hit occurred in
      - edm4hep::Vector3f local             // The local coordinates of the hit in the detector segment [mm]. 
    OneToOneRelations:
      - edm4hep::RawCalorimeterHit rawHit   // Related raw calorimeter hit

  ## ==========================================================================
  ## Clustering
  ## ==========================================================================
  
  edm4eic::ProtoCluster:
    Description: "Collection of hits identified by the clustering algorithm to belong together"
    Author: "S. Joosten"
    OneToManyRelations:
      - edm4eic::CalorimeterHit hits        // Hits associated with this cluster
    VectorMembers:
      - float             weights           // Weight for each of the hits, mirrors hits array

  edm4eic::Cluster:
    Description: "EIC hit cluster, reworked to more closely resemble EDM4hep"
    Author: "W. Armstrong, S. Joosten, C.Peng"
    Members:
      # main variables
      - int32_t           type              // Flag-word that defines the type of the cluster
      - float             energy            // Reconstructed energy of the cluster [GeV].
      - float             energyError       // Error on the cluster energy [GeV]
      - float             time              // [ns]
      - float             timeError         // Error on the cluster time
      - uint32_t          nhits             // Number of hits in the cluster.
      - edm4hep::Vector3f position          // Global position of the cluster [mm].
      - edm4eic::Cov3f    positionError     // Covariance matrix of the position (6 Parameters).
      - float             intrinsicTheta    // Intrinsic cluster propagation direction polar angle [rad]
      - float             intrinsicPhi      // Intrinsic cluster propagation direction azimuthal angle [rad]
      - edm4eic::Cov2f    intrinsicDirectionError // Error on the intrinsic cluster propagation direction
    VectorMembers:
      - float             shapeParameters   // Should be set in metadata, for now it's a list of -- radius [mm], dispersion [mm], 2 entries for theta-phi widths [rad], 3 entries for x-y-z widths [mm].
      - float             hitContributions  // Energy contributions of the hits. Runs parallel to ::hits()
      - float             subdetectorEnergies // Energies observed in each subdetector used for this cluster.
    OneToManyRelations:
      - edm4eic::Cluster        clusters    // Clusters that have been combined to form this cluster
      - edm4eic::CalorimeterHit hits        // Hits that have been combined to form this cluster
      - edm4hep::ParticleID     particleIDs // Particle IDs sorted by likelihood

  ## ==========================================================================
  ## RICH/Cherenkov and PID
  ## ==========================================================================

  edm4eic::PMTHit:
    Description: "EIC PMT hit"
    Author: "S. Joosten, C. Peng"
    Members:
      - uint64_t          cellID            // The detector specific (geometrical) cell id.
      - float             npe               // Estimated number of photo-electrons [#]
      # @TODO do we need an uncertainty on NPE?
      - float             time              // Time [ns]
      - float             timeError         // Error on the time [ns]
      - edm4hep::Vector3f position          // PMT hit position [mm]
      - edm4hep::Vector3f dimension         // The dimension information of the pixel [mm].
      - int32_t           sector            // The sector this hit occurred in
      - edm4hep::Vector3f local             // The local position of the hit in detector coordinates (relative to the sector) [mm]

  edm4eic::CherenkovParticleID:
    Description: "Cherenkov detector PID"
    Author: "A. Kiselev, C. Chatterjee, C. Dilks"
    Members:
      - float             npe               // Overall photoelectron count
      - float             refractiveIndex   // Average refractive index at the Cherenkov photons' vertices
      - float             photonEnergy      // Average energy for these Cherenkov photons [GeV]
    VectorMembers:
      - edm4eic::CherenkovParticleIDHypothesis hypotheses         // Evaluated PDG hypotheses
      - edm4hep::Vector2f                      thetaPhiPhotons    // estimated (theta,phi) for each Cherenkov photon
    OneToOneRelations:
      - edm4eic::TrackSegment                  chargedParticle    // reconstructed charged particle
    OneToManyRelations:
      - edm4eic::MCRecoTrackerHitAssociation   rawHitAssociations // raw sensor hits, associated with MC hits

  edm4eic::RingImage:
    ##@TODO: Juggler support; not used in EICrecon
    Description: "EIC Ring Image Cluster"
    Author: "S. Joosten, C. Peng"
    Members:
      - float             npe               // Number of photo-electrons [#]
      - edm4hep::Vector3f position          // Global position of the cluster [mm]
      - edm4hep::Vector3f positionError     // Error on the position
      - float             theta             // Opening angle of the ring [rad, 0->pi]
      - float             thetaError        // Error on the opening angle
      - float             radius            // Radius of the best fit ring [mm]
      - float             radiusError       // Estimated error from the fit [mm]

  ## ==========================================================================
  ## Tracking
  ## ==========================================================================
  
  edm4eic::RawTrackerHit:
    Description: "Raw (digitized) tracker hit"
    Author: "W. Armstrong, S. Joosten"
    Members:
      - uint64_t          cellID            // The detector specific (geometrical) cell id.
      - int32_t           charge            // ADC value
      ## @TODO: is charge appropriate here? Needs revisiting.
      - int32_t           timeStamp         // TDC value.

  edm4eic::TrackerHit:
    Description: "Tracker hit (reconstructed from Raw)"
    Author: "W. Armstrong, S. Joosten"
    Members:
      - uint64_t          cellID            // The detector specific (geometrical) cell id.
      - edm4hep::Vector3f position          // Hit (cell) position [mm]
      - edm4eic::CovDiag3f positionError    // Covariance Matrix
      - float             time              // Hit time [ns]
      - float             timeError         // Error on the time
      - float             edep              // Energy deposit in this hit [GeV]
      - float             edepError         // Error on the energy deposit [GeV]
    OneToOneRelations:
      - edm4eic::RawTrackerHit rawHit       // Related raw tracker hit
      
  edm4eic::Measurement2D:
    Description: "2D measurement (on an arbitrary surface)"
    Author: "W. Deconinck"
    Members:
      - uint64_t          surface           // Surface for bound coordinates (geometryID)
      - edm4hep::Vector2f loc               // 2D location on surface
      - float             time              // Measurement time
      - edm4eic::Cov3f    covariance        // Covariance on location and time
    VectorMembers:
      - float             weights           // Weight for each of the hits, mirrors hits array
    OneToManyRelations:
      - edm4eic::TrackerHit hits            // Hits in this measurement (single or clustered)

  edm4eic::TrackSeed:
    Description: "Seed info from the realistic seed finder"
    Author: "S. Li, B. Schmookler, J. Osborn"
    Members:
      - edm4hep::Vector3f         perigee   // Vector for the perigee (line surface)
    OneToManyRelations:
      - edm4eic::TrackerHit       hits      // Tracker hits triplet for seeding
    OneToOneRelations:
      - edm4eic::TrackParameters  params    // Initial track parameters
      
  edm4eic::Trajectory:
    Description: "Raw trajectory from the tracking algorithm. What is called hit here is 2d measurement indeed."
    Author: "S. Joosten, S. Li"
    Members:
      - uint32_t          type              // 0 (does not have good track fit), 1 (has good track fit)
      - uint32_t          nStates           // Number of tracking steps
      - uint32_t          nMeasurements     // Number of hits used 
      - uint32_t          nOutliers         // Number of hits not considered 
      - uint32_t          nHoles            // Number of missing hits
      - uint32_t          nSharedHits       // Number of shared hits with other trajectories
    VectorMembers:
      - float             measurementChi2   // Chi2 for each of the measurements
      - float             outlierChi2       // Chi2 for each of the outliers
    OneToManyRelations:
      - edm4eic::TrackParameters trackParameters            // Associated track parameters, if any
      - edm4eic::Measurement2D measurements_deprecated      // Measurements that were used for this track. Will move this to the edm4eic::Track
      - edm4eic::Measurement2D outliers_deprecated          // Measurements that were not used for this track. Will move this to the edm4eic::Track
    OneToOneRelations:
      - edm4eic::TrackSeed      seed      // Corresponding track seed

  edm4eic::TrackParameters:
    Description: "ACTS Bound Track parameters"
    Author: "W. Armstrong, S. Joosten, J. Osborn"
    Members:
      - int32_t              type              // Type of track parameters (-1/seed, 0/head, ...)
      - uint64_t             surface           // Surface for bound parameters (geometryID)
      - edm4hep::Vector2f    loc               // 2D location on surface
      - float                theta             // Track polar angle [rad]
      - float                phi               // Track azimuthal angle [rad]
      - float                qOverP            // [e/GeV]
      - float                time              // Track time [ns] 
      - int32_t              pdg               // pdg pid for these parameters
      - edm4eic::Cov6f       covariance        // Full covariance in basis [l0,l1,theta,phi,q/p,t]


  edm4eic::Track:
    Description: "Track information at the vertex"
    Author: "S. Joosten, J. Osborn"
    Members:
      - int32_t            type                           // Flag that defines the type of track
      - edm4hep::Vector3f  position                       // Track 3-position at the vertex 
      - edm4hep::Vector3f  momentum                       // Track 3-momentum at the vertex [GeV]
      - edm4eic::Cov6f     positionMomentumCovariance     // Covariance matrix in basis [x,y,z,px,py,pz]
      - float              time                           // Track time at the vertex [ns]
      - float              timeError                      // Error on the track vertex time
      - float              charge                         // Particle charge
      - float              chi2                           // Total chi2
      - uint32_t           ndf                            // Number of degrees of freedom
      - int32_t            pdg                            // PDG particle ID hypothesis
    OneToOneRelations:
      - edm4eic::Trajectory                     trajectory      // Trajectory of this track
    OneToManyRelations:
      - edm4eic::Measurement2D measurements      // Measurements that were used for this track
      - edm4eic::Track      tracks            // Tracks (segments) that have been combined to create this track

  edm4eic::TrackSegment:
    Description: "A track segment defined by one or more points along a track."
    Author: "S. Joosten"
    Members:
      - float             length            // Pathlength from the first to the last point
      - float             lengthError       // Error on the segment length
    OneToOneRelations:
      - edm4eic::Track    track             // Track used for this projection
    VectorMembers:
      - edm4eic::TrackPoint points          // Points where the track parameters were evaluated

  ## ==========================================================================
  ## Vertexing
  ## ==========================================================================

  edm4eic::Vertex:
    Description: "EIC vertex"
    Author: "J. Osborn"
    Members:
      - int32_t             type          // Type flag, to identify what type of vertex it is (e.g. primary, secondary, generated, etc.)
      - float               chi2          // Chi-squared of the vertex fit
      - int                 ndf           // NDF of the vertex fit
      - edm4hep::Vector4f   position      // position [mm] + time t0 [ns] of the vertex. Time is 4th component in vector
      ## this is named "covMatrix" in EDM4hep, renamed for consistency with the rest of edm4eic
      - edm4eic::Cov4f      positionError // Covariance matrix of the position+time. Time is 4th component, similarly to 4vector 
    OneToManyRelations:
      - edm4eic::ReconstructedParticle associatedParticles // particles associated to this vertex.

  ## ==========================================================================
  ## Kinematic reconstruction
  ## ==========================================================================

  edm4eic::InclusiveKinematics:
    Description: "Kinematic variables for DIS events"
    Author: "S. Joosten, W. Deconinck"
    Members:
      - float             x                 // Bjorken x (Q2/2P.q)
      - float             Q2                // Four-momentum transfer squared [GeV^2]
      - float             W                 // Invariant mass of final state [GeV]
      - float             y                 // Inelasticity (P.q/P.k)
      - float             nu                // Energy transfer P.q/M [GeV]
    OneToOneRelations:
      - edm4eic::ReconstructedParticle scat // Associated scattered electron (if identified)
      ## @TODO: Spin state?
      ## - phi_S?

  edm4eic::HadronicFinalState:
    Description: "Summed quantities of the hadronic final state"
    Author: "T. Kutz"
    Members:
      - float             sigma             // Longitudinal energy-momentum balance (aka E - pz)
      - float             pT                // Transverse momentum
      - float             gamma             // Hadronic angle
    OneToManyRelations:
      - edm4eic::ReconstructedParticle hadrons // Reconstructed hadrons used in calculation

  ## ==========================================================================
  ## Data-Montecarlo relations
  ## ==========================================================================

  edm4eic::MCRecoParticleAssociation:
    Description: "Used to keep track of the correspondence between MC and reconstructed particles"
    Author: "S. Joosten"
    Members:
      - uint32_t          simID             // Index of corresponding MCParticle (position in MCParticles array)
      - uint32_t          recID             // Index of corresponding ReconstructedParticle (position in ReconstructedParticles array)
      - float             weight            // weight of this association
    OneToOneRelations :
      - edm4eic::ReconstructedParticle rec  // reference to the reconstructed particle
      - edm4hep::MCParticle sim             // reference to the Monte-Carlo particle

  edm4eic::MCRecoClusterParticleAssociation:
    Description: "Association between a Cluster and a MCParticle"
    Author : "S. Joosten"
    Members:
      - uint32_t          simID             // Index of corresponding MCParticle (position in MCParticles array)
      - uint32_t          recID             // Index of corresponding Cluster (position in Clusters array)
      - float             weight            // weight of this association
    OneToOneRelations:
      - edm4eic::Cluster  rec               // reference to the cluster
      - edm4hep::MCParticle sim             // reference to the Monte-Carlo particle

  edm4eic::MCRecoTrackParticleAssociation:
    Description: "Association between a Track and a MCParticle"
    Author : "S. Joosten"
    Members:
      - uint32_t          simID             // Index of corresponding MCParticle (position in MCParticles array)
      - uint32_t          recID             // Index of corresponding Track (position in Tracks array)
      - float             weight            // weight of this association
    OneToOneRelations:
      - edm4eic::Track    rec               // reference to the track
      - edm4hep::MCParticle sim             // reference to the Monte-Carlo particle

  edm4eic::MCRecoVertexParticleAssociation:
    Description: "Association between a Vertex and a MCParticle"
    Author : "S. Joosten"
    Members:
      - uint32_t          simID             // Index of corresponding MCParticle (position in MCParticles array)
      - uint32_t          recID             // Index of corresponding Vertex (position in Vertices array)
      - float             weight            // weight of this association
    OneToOneRelations:
      - edm4eic::Vertex     rec             // reference to the vertex
      - edm4hep::MCParticle sim             // reference to the Monte-Carlo particle

  edm4eic::MCRecoTrackerHitAssociation:
    Description: "Association between a RawTrackerHit and a SimTrackerHit"
    Author: "C. Dilks, W. Deconinck"
    Members:
      - float                 weight        // weight of this association
    OneToOneRelations:
      - edm4eic::RawTrackerHit rawHit       // reference to the digitized hit
      - edm4hep::SimTrackerHit simHit       // reference to the simulated hit

  edm4eic::MCRecoCalorimeterHitAssociation:
    Description: "Association between a RawCalorimeterHit and a SimCalorimeterHit"
    Author: "S. Rahman"
    Members:
      - float                 weight        // weight of this association
    OneToOneRelations:
      - edm4hep::RawCalorimeterHit rawHit   // reference to the digitized calorimeter hit
      - edm4hep::SimCalorimeterHit simHit   // reference to the simulated calorimeter hit

  edm4eic::TrackClusterMatch:
    Description: "Match between a Cluster and a Track"
    Author: "D. Anderson, D. Brandenburg, D. Kalinkin, S. Joosten"
    Members:
      - float                 weight        // weight of this association
    OneToOneRelations:
      - edm4eic::Cluster  cluster           // reference to the cluster
      - edm4eic::Track track                // reference to the track