AOD producer: improve MC collision labels for embedded events#15299
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sawenzel wants to merge 1 commit intoAliceO2Group:devfrom
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AOD producer: improve MC collision labels for embedded events#15299sawenzel wants to merge 1 commit intoAliceO2Group:devfrom
sawenzel wants to merge 1 commit intoAliceO2Group:devfrom
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In embedding scenarios where a single background event is reused across multiple collisions, e.g.: Collision 0: Background 0 + Signal 0 Collision 1: Background 0 + Signal 1 Collision 2: Background 0 + Signal 2 Collision 3: Background 0 + Signal 3 Collision 4: Background 0 + Signal 4 the primary vertexer may return MC labels all pointing to "Background 0". This caused an ambiguous lookup in the AOD producer, resulting in all reconstructed collisions being incorrectly associated to the same MCCollision entry. This is addressed by collecting all MCCollision candidates matching a given (sourceID, eventID) label and disambiguating via bunch-crossing time, picking the MCCollision whose BC is closest to the reconstructed vertex time. Note: a more robust long-term solution would be to extend the primary vertexer to return the full set of contributing MC labels per found vertex, enabling simpler and more reliable disambiguation strategies. This relates to https://its.cern.ch/jira/browse/O2-6840.
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@sawenzel currently the PVertex MCEventLabel follows the same schema as for other reconstructed objects: it corresponds to the label of the majority of contributors (additionally storing also the fraction of this majority). |
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In embedding scenarios where a single background event is reused across multiple collisions, e.g.:
Collision 0: Background 0 + Signal 0
Collision 1: Background 0 + Signal 1
Collision 2: Background 0 + Signal 2
Collision 3: Background 0 + Signal 3
Collision 4: Background 0 + Signal 4
the primary vertexer may return MC labels all pointing to "Background 0". This caused an ambiguous lookup in the AOD producer, resulting in all reconstructed collisions being incorrectly associated to the same MCCollision entry.
This is addressed by collecting all MCCollision candidates matching a given (sourceID, eventID) label and disambiguating via bunch-crossing time, picking the MCCollision whose BC is closest to the reconstructed vertex time.
Note: a more robust long-term solution would be to extend the primary vertexer to return the full set of contributing MC labels per found vertex, enabling simpler and more reliable disambiguation strategies.
This relates to https://its.cern.ch/jira/browse/O2-6840.