Purpose of this page:

Give details of the persistent data object produced during track reconstruction and their usage. This page documents the configuration file RecoTrack_EventContent.cff.

Event Content

Tracking Products

The track producer in CMSSW gives the following products
  • collection of the reco::Track
    This class (despite the profusion of member function) only owns the following data member
    • reference to the associated track extra.
      However, the TrackBase class from which it derives own the following members
    • 3-momentum at the point of reference: point of transverse closest approach as defined by TrajectoryStateClosestToPoint
    • the reference point at which the track parameters are given
    • chi square value, and the number of degrees of freedom.
    • the charge
    • 15 independent terms of the error matrix
    • the compress data format of the reconstructed HitPattern

  • collection of the reco::TrackExtra referenced by the reco::Track.
    This class owns the following data members
    • momentum, position, 15 indepenent terms of error matrix and detector id at the innermost measurement.
    • momentum, position, 15 indepenent terms of error matrix and detector id at the outermost measurement.
      The class reco::TrackExtraBase which it inherits from own the following members
    • collection of reference to the reconstructed hits on the track. The actual collection of reconstructed hits is supposedly produced separately (see below).
  • collection of the reco::TrackingRecHit used on the reconstructed tracks

Additional side products are put in the event as transient product depending on the track reconstruction algorithm considered (Ckf, GSF, RS, ...). These products are not written to disk.


The root files produced and labelled RECO are made for re-reconstruction or reconstruction validation purpose. They contain most of information produced during track final fit. Full access to reconstructed hits and inner/outer measurement information is possible. Full track refit is also possible. It might not be possible to redo pattern recognition since it depends on some lower level products that are not discussed here. Do not assume you can redo it from RECO root files. (choose DIGI files instead).


The root files produced with label AOD are made for analysis purpose and do not contain all the event information because of disk space limitation. The tracking information is skimmed down to only the collection of reco::Track. What can be accessed on AOD is
  • momentum, position, charge at the reference point (point of transverse closest approach)
  • chi square value, and the number of degrees of freedom.
  • the compress data format of the reconstructed hits used, which does not provide any 3-momentum information.
The user should be aware that none of the TrackExtra information (see above) is available on AOD, even if the reco::Track provides member function to access it. Using reco::Track::innerMomentum() for example will result in de-referencing the TrackExtraRef and the subsequent framework exception for a missing products.

-- JeanrochVlimant - 01 Dec 2007

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Topic revision: r4 - 2009-02-17 - KatiLassilaPerini
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