- Algorithm or Service name
- EM Shower
- Author or Maintainer
- Mike Wallbank
- one line description
- 3D shower reconstruction algorithm which takes 2D clusters in each view and produces 3D shower objects with all relevant properties
The EMShower algorithm takes 2D clusters and associated hits (previously found by e.g. BlurredCluster) and 3D tracks (previously found by e.g. PMTrack) and outputs 3D showers (recob::Showers), along with associated hits, clusters and tracks, to the event. It is written as an extension of the BlurredCluster algorithm (description here) and simply matches these already complete clusters between the views to produce 3D shower objects. It is intended to be very high level and relies on other reconstruction to have already been performed.
The reconstruction proceeds in the following general steps:
- The 2D BlurredClusters and 3D tracks, along with their hit associations, are taken from the event.
- By using the associated hits from the tracks with the clusters in each view, the clusters are matched between the views to form 3D objects comprised of hits from each view. This is the only object reconstruction performed; everything that follows is only to find the properties of the showers.
- The properties of these showers are determined by a variety of algorithms which are applied to this hit selection. Properties we require are shower direction and start point, dE/dx and total deposited energy.
- First, the two ends of the shower are found in each view (one being the true start point). The hits are then oriented correctly along the length of the shower in order to identify which end is the start. An initial track is reconstructed from this start point in each view and then used to construct a recob::Track. From this track, the start point and direction can be determined. dE/dx and total energy of the shower are used by analysing the ordered hits with standard calorimetry reconstruction. The best plane is determined to be the one with the greatest number of hits.
- The output back into the event are recob::Shower objects, along with associated recob::Hits, recob::Clusters and recob::Tracks.
See the document attached (below) for a more complete description of the algorithm.
- location in code
- 3D hit reconstruction, other
- code analysis done
- improved code released