I am sorry for the confusion - my explanation was also not completely correct. In RecoTauTag/RecoTau/src/RecoTauConstructor.cc you can see how they are accessed. The SignalPFChardedHadrons are fillied in RecoTauTag/RecoTau/plugins/RecoTauBuilderCombinatoricPlugin.cc (function addPFCand defined in RecoTauConstructor) They contain all charged PFCands (i.e. charged h, e and mu). The SignalGamma are filled by function addPiZeros. We build PiZero collection from "gamma" candidates (i.e. PFGammas and PFElectrons) and the function I mention saves the daughters of this composite particles, so in principle PFGammas and PFElectrons. PFNeutralHadrons is unused at the moment, but is there for possible future use. SignalPFCands is then accessor to all 3 other collections combined.