MCH Geometry Transformations

Here you will find functions to perform transformations on MCH geometry : local to global, global to local, and various (mis)alignement ones.

MCH Transformations in JSON format

Also available is a CLI utility to extract MCH transformations (rotations and translations) from a Root geometry file and export them in JSON format :

o2-mch-convert-geometry --geom o2sim_geometry.root > geom.json

The JSON output is compact on purpose, to save some space (e.g. on github).

But as any JSON it can be manipulated further with e.g. jq

For instance you can pretty-print it :

cat output.json | jq .

Or sort the output per detection element id :

cat output.json | jq '.alignables|=sort_by(.deid)'

That last command being the one that was used to produce the example ideal-geometry-o2.json file.

Workflow

The o2-mch-clusters-transformer-workflow takes as input the list of all clusters (Cluster), in local reference frame, in the current time frame, with the data description "CLUSTERS".

It sends the list of the same clusters, but converted in global reference frame, with the data description "GLOBALCLUSTERS".

By default the workflow reads the (aligned) geometry from the CCDB. One can instead read the geometry from a file (either JSON or Root format) using the --geometry option, together with the explicit --mch-disable-geometry-from-ccdboption.

To test it one can use e.g. a sampler-transformer-sink pipeline as such :

o2-mch-clusters-sampler-workflow
    -b --nEventsPerTF 1000 --infile someclusters.data |
o2-mch-clusters-transformer-workflow
    -b --mch-disable-geometry-from-ccdb --geometry Detectors/MUON/MCH/Geometry/Test/ideal-geometry-o2.json |
o2-mch-clusters-sink-workflow
    -b --txt --outfile global-clusters.txt --no-digits --global