Left: \tr trigger efficiency for inclusive clusters and isolated-narrow clusters with $R=0.2$ (similar for $R=0.4$) obtained with PYTHIA~8 simulations combining $\gamma$--jet and jet--jet processes, embedded in data in the considered centrality class for \PbPb collisions and considering the corresponding trigger thresholds ($E_{\rm trig}$) in each system. Right: \tr trigger rejection factor calculated by applying the trigger efficiency for \pp collisions and for each of the \PbPb centrality classes considered. Solid lines over points result from a constant fit, values given in Table~\ref{tab:Lumi}, dashed lines indicate the fit uncertainty obtained with the procedure explained in Sect.~\ref{sec:sys_unc}. For clusters above 12~\GeVc and peripheral \PbPb collisions, the rejection factor and trigger efficiency are calculated for the sum of the two triggered samples with thresholds at 5 and 10 GeV.