Collections and roles¶

A DELPHI edm4hep file offers many collections of each kind. Entry 3990 of Y13709.126.edm4hep.root holds 67 collections, 27 of them populated:

EDM4hep type	how many	examples (objects in that event)
`ParticleID`	24	`sDST_HAID_HadronID` (19), `sDST_BBDXGET_Dedx` (17), `sDST_AABTAG_TrackTag` (15)
`Vertex`	7	`sDST_AABTAG_PrimaryVertex` (1), `sDST_AABTAG_SecondaryVertices` (2), `sDST_V0_V0Candidates` (4), `sDST_PV_Vertices` (4)
`Cluster`	4	`sDST_EMNC_Showers` (18), `sDST_HCNC_Showers` (0)
`Track`	3	`sDST_TRAC_Tracks` (19), `sDST_ELTR_RefitTracks` (5)
`TrackerHit3D`	2	`sDST_TDVD_VDHits` (79), `sDST_TDVD_VDPoints` (65)

Pinning one of each by name would show a single arbitrary slice, so the display does not.

Roles¶

schema.read_schema reads podio's podio_metadata — the same source the converter's collection map is built from — and Schema.resolve binds each role to a collection using the preference lists in schema.ROLES:

role	EDM4hep type	default preference
`particles`	`ReconstructedParticle`	`*MAIN_Particles`
`tracks`	`Track`	`*TRAC_Tracks`
`jets`	`ReconstructedParticle`	`*_Jets`
`primary_vertex`	`Vertex`	`AABTAG_PrimaryVertex`, `PV_PrimaryVertex`
`secondary_vertices`	`Vertex`	`*AABTAG_SecondaryVertices`
`em_clusters`	`Cluster`	`*EMNC_Showers`
`vd_hits`	`TrackerHit3D`	`*TDVD_VDHits`
`hadron_id`	`ParticleID`	`*HAID_HadronID`

A populated collection beats an empty one of the same rank. The historical DELPHI names are simply the first preference, so defaults reproduce the original display exactly.

Override from the command line:

delphi-display FILE --entry 3990 --out e.html \
  --collection vd_hits=sDST_TDVD_VDPoints \
  --collection secondary_vertices=sDST_V0_V0Candidates

or from Python:

e = read_event(path, 3990, collections={"vd_hits": "sDST_TDVD_VDPoints"})

or with the dropdowns in the app.

Provenance and domains¶

Provenance comes from the file itself: each collection is transcribed from a DST bank, derived by SKELANA at conversion time, or custom to the converter.

Domains are the one field podio does not carry. They are taken from the converter's published collection map and shipped as docs/collection_domains.json.

The published map can lag the file

The map describes 64 collections; this file has 67. sDST_AABTAG_SecondaryVertices, sDST_AABTAG_Jets and sDST_AABTAG_JetTag — which the display depends on — are not in it, so they show as domain unknown. Regenerate the map from the converter to fix that.