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Charge conjugation C is one of the fundamental symmetries in nature whichtransforms particles into antiparticles. This symmetry was studied in weakinteraction where it is fully violated, but it is poorly known in the strongand electromagnetic interactions.  To this end, in this thesis we investigated eta->pi+pi-pi0 and eta->pi0 e+e-decays, which might violate charge conjugation symmetry. The violation of Csymmetry in eta->pi+pi-pi0 process could manifest itself as an asymmetrybetween energy spectra of charged pions. The eta->pi0 e+e- decay is forbiddenby C symmetry in the first order of electromagnetic interaction, with thebranching ratio on a level of 10^-8. Therefore, observation of a largerbranching ratio could indicate a mechanism involving first orderelectromagnetic interaction violating charge conjugation.  Both decays were investigated by means of the WASA-at-COSY detector operatingat the COSY synchrotron at the Forchungszentrum Julich in Germany. The etameson was produced via pp->pp eta reaction at the proton beam momentum of2.14GeV/c. In total around 5x10^7 eta mesons were collected.  As a result of the analysis conducted in the framework of this thesis aDalitz Plot distribution for the eta->pi+pi-pi0 decay was obtained. From thisdistribution we extracted asymmetry parameters sensitive to C symmetryviolation for different isospin values of the final state and we haveestablished that all are consistent with zero within the obtained accuracy.  For the eta->pi0 e+e- decay we have not observe signal and thus we estimatedan upper limit for the branching ratio. The established upper limit amounts to$BR(eta->pi0 e+e-)<3.7x10^-5 at the 90% confidence level. This result is moreprecise than previously obtained in other experiments.

Test of charge conjugation invariance in eta->pi0 e+e- and eta->pi+pi-pi0 decays