Upper panel: Correlation of ZDC and the VZERO response in hadronic collisions Lower panel: Distribution of the sum of amplitudes in the VZERO scintillator tiles (black histogram); inset shows the low amplitude part of the distribution The red line shows the fit of the Glauber calculation to the measurement The fit was performed above the cut indicated in the inset, avoiding the region at low amplitudes dominated by the electromagnetic processes The shaded area corresponds to the most central 5% of hadronic collisions