In event-based reconstruction, raw event building (from digis) is the first step, after which reconstruction is applied for each event. Currently, we do not have a real raw event builder; we employ the ideal event builder using MC truth information.
The relevant task class is CbmBuildEventsIdeal (in reco/eventbuilder/digis). The current implementation uses the MC event number of the link with the largest weight in the digi match object.
Deficiency: With the introduction of embedding and mixing in digitization, there can be multiple MC input files, each with their own sequence of event number (entries). The variable CbmLink::GetEntry() is thus not sufficient to unambiguously identify a MC event.
Solution: The current class shall be extended to use the combination of input number (CbmLink::GetFile()) and event number (CbmLink::GetEntry()) to attribute digi objects to events.