The dependences of energy distributions in FHCal modules on the polar
angle and on the centrality were studied. They allow the construction of a
few observables as transverse and longitudinal energies. The fit of
angular distributions by the linear function on the event-by-event basis
allows to extract the transverse gradient of the spectator energy in the
calorimeter and also the energy carried by free spectators inside the beam
hole. The clear correlations between the fit parameters are observed in
full range of the collision centralities.
Assuming, that the peripheral area of FHCal is occupied mainly by the
non-spectator’s particles, their energy contribution to the full FHCal
energy was subtracted. It makes possible to avoid the ambiguity in FHCal
energy depositions for central and peripheral events. The developed
approaches are used for the determination of the collision centrality with
FHCal alone without application of TPC information on multiplicity.
