  It is known that the Standard Model does not describe all phenomena related
to subatomic particles. This thesis presents feasibility studies of the
measurement of eta meson decay using WASA-at-COSY detector which tests
predictions of the Standard Model. The aim of this thesis is to estimate the
time of measurement for which the current branching ratio limit of eta -> 4pi0
decay can be improved. In order to estimate the time of measurement Monte Carlo
simulations were performed. Kinematics of the pp -> ppeta -> pp4pi0 -> pp8gamma
reactions were simulated using PLUTO program. Next, by means of the GEANT3
program the response of the WASA-at-COSY detector was simulated for each
particle. Received signals were analysed in RootSorter software package based
on ROOT. Studies of the reaction with many gamma quanta in the exit channel
required the investigation of WASA-at-COSY calorimeter functioning. Tests of a
cluster building algorithm with emphasis on merging and splitting of detected
signals were done. The obtained result shows that only about 3% of eta -> 4p0
decays can be properly reconstructed. The identification of the eta -> 4pi0 ->
8gamma decay was based on the invariant mass method for both pi0 and eta
mesons. As a result, the resolution of the invariant mass determination of the
eta meson was established to sigma = 31 MeV/c2. The acceptance of the
WASA-at-COSY detector for pp -> ppeta -> pp4pi0 -> pp8gamma reaction was
determined to Aeta=(Neta detected) / (Neta produced) = 1.5%. The time of
measurement for obtaining a statistical precision equal to the current
branching ratio limit for Tbeam = 1.3 GeV is about 13 hours. It was also
established that the lower the excess energy in the eta production is the
shorter the time of the measurement needed.
