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It is known that the Standard Model does not describe all phenomena relatedto subatomic particles. This thesis presents feasibility studies of themeasurement of eta meson decay using WASA-at-COSY detector which testspredictions of the Standard Model. The aim of this thesis is to estimate thetime of measurement for which the current branching ratio limit of eta -> 4pi0decay can be improved. In order to estimate the time of measurement Monte Carlosimulations were performed. Kinematics of the pp -> ppeta -> pp4pi0 -> pp8gammareactions were simulated using PLUTO program. Next, by means of the GEANT3program the response of the WASA-at-COSY detector was simulated for eachparticle. Received signals were analysed in RootSorter software package basedon ROOT. Studies of the reaction with many gamma quanta in the exit channelrequired the investigation of WASA-at-COSY calorimeter functioning. Tests of acluster building algorithm with emphasis on merging and splitting of detectedsignals were done. The obtained result shows that only about 3% of eta -> 4p0decays can be properly reconstructed. The identification of the eta -> 4pi0 ->8gamma decay was based on the invariant mass method for both pi0 and etamesons. As a result, the resolution of the invariant mass determination of theeta meson was established to sigma = 31 MeV/c2. The acceptance of theWASA-at-COSY detector for pp -> ppeta -> pp4pi0 -> pp8gamma reaction wasdetermined to Aeta=(Neta detected) / (Neta produced) = 1.5%. The time ofmeasurement for obtaining a statistical precision equal to the currentbranching ratio limit for Tbeam = 1.3 GeV is about 13 hours. It was alsoestablished that the lower the excess energy in the eta production is theshorter the time of the measurement needed.

Feasibility study of measuring CP symmetry violation via eta->4pi decay using WASA-at-COSY detector