Enhancement: Interested in contributing EDM4hepLoader

I don't have any TypeScript experience :-) but I'm interested in contributing an event loader for the EDM4hep data model used by the key4HEP project. The data model contains both simulated and reconstructed quantities which would be useful to implement, but an initial goal is these simulated quantities:

• MCParticles (which could be loaded as 'truth' tracks)
• SimTrackerHits
• SimCalorimeterHits

My approach would be to use the ScriptLoader to use JSROOT to read edm4hep.root files.

The EDM4hep data model does not contain geometry information beyond position (and in some cases momentum). Connection to geometry is done through the cellID fields which connect to DD4hep geometry objects. This will not be possible to replicate here unless there is some way of connecting the cellID back to the geometry in Phoenix. That's out of scope here (and likely not necessary until we need to show entire calorimeter blocks instead of simple hit positions).

The files in the EDM4hep data model do not use prescribed names for the collections of event-level information. A SimTrackerHits collection can be stored under any name, which will need to be defined in the event loader configuration (MCParticles are typically stored under that name, though, so it presents a convenient target for initial implementation).

Cc'ing @vvolkl since of interest.

Start by examining the existing ScriptLoader and its use of JSROOT for reading event data. Define how configurable collection names should be supplied, then scope initial support for MCParticles, SimTrackerHits, and SimCalorimeterHits; geometry and cellID connections are explicitly out of scope. Done means these collections can be loaded from EDM4hep ROOT files for display.