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0001 # Event data
0002
0003 :::{attention}
0004 This section is **incomplete!**
0005 :::
0006
0007 :::{toctree}
0008 :maxdepth: 1
0009 parametrization
0010 tracks
0011 measurements
0012 particle_hypothesis
0013 :::
0014
0015 The various tracking components in ACTS can be assembled into a full
0016 reconstruction chain. Between these components, data needs to be exchanged in
0017 a well-defined way. This is achieved through the {term}`EDM` (Event Data Model), which
0018 is a set of data types and interfaces representing the content of an event.
0019 Until very recently, ACTS has focused mainly on an *internal* {term}`EDM`, which
0020 is really focused on efficient interchange between components inside the
0021 toolkit, sometimes at the cost of usability for clients. With the main
0022 reconstruction chain becomes more and more mature, however, the focus has
0023 shifted to a more client-oriented {term}`EDM` encapsulating the outputs of tracking.
0024
0025 (edm_chain)=
0026 :::{figure} figures/edm_chain.svg
0027 :width: 100%
0028 Diagram showing the stages and data flow of a track reconstruction chain. The
0029 boxes show {term}`EDM` objects that are passed between the stages.
0030 :::
0031
0032
0033 {numref}`edm_chain` shows an overview of the {term}`EDM` data types and how
0034 they form a data-flow sequence. Measurements coming from the experiment
0035 software are the main inputs of the chain. This data-type is abstracted in ACTS
0036 in a way that allows the details of these measurements to be fully
0037 experiment-specific. See [](#edm_uncalib_meas) for details.
0038
0039 ACTS ships with a clusterization algorithm, which can turn segmented raw
0040 measurements into clusters, the second {term}`EDM` object in the chain,
0041 representing particle intersections with the sensors. For the creation of track
0042 seeds, clusters need to be converted into three-dimensional space-points,
0043 combining information from multiple clusters where needed, e.g. for
0044 one-dimensional silicon strip sensors. The space-points and seeds are part of
0045 the {term}`EDM` as well, since they are handed over to the track finding
0046 component. This component is responsible for the creation of completed tracks,
0047 which can then optionally be refitted with a precision track fitter.
0048
0049 Both the track finding and the precision track fit produce track objects, which
0050 are the primary output of the tracking chain. More on the track EDM can be
0051 found in [](#edm_tracks).
