/** Method to retrieve the <Identifier, InDetSimData> maps for Pixel,SCT,TRT;
* returns true if at least one map was found */
boolGetTruthMaps();
/** Add to map (hits_map) of <GenParticle,nr.of hits> all the GenParticles from vector (p_vec) which are not yet in the map; for those which are, increment numbers of hits */