  The work was carried out in the framework of the KLOE collaboration studying
the decays of the phi meson produced in the DAFNE accelerator in the collisions
of electron and positron. The main aim of this thesis was investigation of the
influence of the merging and splitting of clusters in decays with the high
multiplicity of gamma quanta, which are at most biased by these effects. For
this aim we implemented the full geometry and realistic material composition of
the barrel electromagnetic calorimeter in FLUKA package. The prepared Monte
Carlo based simulation program permits to achieve a fast generation of the
detector response separately for each interested reaction. The program was used
to study the reconstruction efficiency with the KLOE clustering algorithm as a
function of the photocathode quantum efficiency. It was also used to
investigate merging and splitting probabilities as a function of the quantum
efficiency. The conducted studies indicated that the increase of quantum
efficiency does not improve significantly the identification of clusters. The
influence of these effects was estimated for eta meson decays into 3 neutral
pions and K_short meson into 2 neutral pions.
