\ \ptIsoCh\ distribution for narrow clusters with $0.1\sigmalongPb0.3$ for $\pt > 16$ GeV/$c$,in \pp (lower right frame) and \PbPb collisions in five centrality classes, with $R=0.2$ (black bullets) and $R=0.4$ (blue squares),in data (full markers) and simulated PYTHIA 8 $\gamma$--jet processes (open markers), embedded into data in case of \PbPb collisions.