EGamma Geant4 thinning master [ATLSWUPGR-150]
Master companion of !51105 (merged)
Following some observations discussed in ATLSWUPGR-150, it was noticed that a different treatment was applied for the MCTruthClassification of central electrons (track-based) and forward electrons (cluster-based in the current implementation but ultimately track-based once upgrade developments have advanced). In particular, the truth-matching for forward electrons discard Geant4 particle as valid match while this is not the case for central electrons. This difference leads to a much larger number of EGamma truth objects in the central region after the Geant4 thinning is applied in the ESDtoAOD step. This MR aims at making the behaviour more consistent between the central and the forward region for the Run4 configuration, by disabling the discarding of Geant4 particle for forward electrons + adapt a truth eta cut to the ITk acceptance in the Geant4 thinning algorithm.
Note that this could in particular also be applied to Run2-3 config but I prefer not to interfere there, considering the ongoing production effort and this would increase the size of the TruthParticle container in AOD + potentially impact EGamma performance studies in the forward regions depending on how they are set up exactly.