This thesis is a groundwork for a search for the C-violating φ → ωγ decay and the rare ω → l+l−π0 decay with the KLOE detector. A feasibility study of the detection acceptance for the ω → π+π−π0 and ω → l+l−π0 decays produced in the e+e− → ωγISR and e+e− → ωπ0 production channels. A study of the main background to the forbidden φ decay, the e+e− → ωγISR process, is performed using a data sample with an integrated luminosity of L = 1.6 fb−1 collected by the KLOE detector at center of mass energy √s = 1019 MeV. / Walter Andersson