In this thesis the Dalitz decays of the pion, eta and omega-meson have been studied in photon induced reactions off the proton. The main aim has been to determine the electro-magnetic transition form factor of the eta-meson. This form factor provides significant information about the electromagnetic properties of this meson. As a meson is a non-point like particle, the corresponding electro-magnetic transition form factor is expected to differ from the standard QED prediction (Quantum Electro Dynamics). Hence, a measurement of this form factor provides the possibility to investigate this deviation from the QED and to test theoretical models like the (Vector Meson Dominance Model) VMD or the model by Leupold-Terschluesen.Beside the Dalitz decays other decay modes of the eta and the omega-meson were analyzed and the branching ratios of the decays eta->pi+pi-pi0, eta-Dalitz and omega->gamma+pion were determined. Furthermore the cross section of -production as well as the cross section of pion-eta-production in photon induced reactions off the proton were determined. Another aspect of this work was to investigate the possibility of separating electrons and positrons from charged pions with the Crystal Ball and TAPS detector systems at MAMI-C in Mainz. This coupled detector-setup is very efficient in detecting photons and thus it is particularly suited for measure-ments of neutral decay modes of hadrons. As this setup does not use a magnetic field, an accurate separation of electrons/positrons from charged pions is difficult. However, it was shown in this work, that an accurate separation and identification of those particles is possible by exploiting the full kinematic information available in ex-clusive analyses. Thereby Dalitz decays were identified. The background from charged pions was suppressed further. Moreover it was found that cuts on the cluster sizes of the charged hits further suppress the charged pion background. The pro-bability for the misidentification of a charged pion-pair as an electron/positron-pair is less than 3 10^(-7).The experimental data were taken during two beamtimes in 2007 at the electron acceleration facility MAMI-C in Mainz. Energy tagged photons pro-duced via the bremsstrahlung process impinged on a liquid hydrogen target and induced among others the reactions of interest. The detectors Tagger, Crystal Ball (including the PID) and TAPS (including the VETO) were used for data recording. A preliminary particle identification was provided by the dE-versus-E and the time-of-flight method. Furthermore the information about time-coincidences between detected hits were exploited in order to suppress random events. The total amount of experimental raw data was approximately 2 TByte. Therefore a compression of the data was necessary. For this purpose a ntuple-based analysis procedure was developed. Only events fulfilling certain requirements were saved to these ntuples. Thus the original amount of data was significantly reduced. Before this compression, the data had been calibrated by the A2-group of the University of Giessen. In this respect many procedures, macros and programs had to be developed from scratch. The same holds for the subsequent analysis of the data. A new analysis program called AR2v3 was developed in C++. In all analyses the detection of the meson and the recoiling proton was required; thus the full kinematic information could be exploited. Cuts were applied on the energy balance, momentum balance, missing mass and the coplanarity. Depending on the particular decay channel further cuts were applied on the relative angle between particles, the incident energy, the -angle of the proton and if applicable on the cluster sizes of the charged hits. The applied cuts were verified by displaying each variable under the constraint of all other cuts. Besides the analysis of experimental data sim-ulated data were analyzed in order to determine the detector response. The simulated data were produced by a Monte-Carlo simulation which contained the full detector setup. The corresponding start distributions for the simulation were generated using a phase space event generator as well as the PLUTO event generator. In the exclusive analysis of the eta-Dalitz decay 827 events were reconstructed. This is an improvement by a factor 8 with respect to the measurement by the SND collaboration. The slope parameter of the associated transition form factor was determined asb = dF/dq2 |q2=0 = Lambda^(-2) = (1.84 + 0.43 − 0.32) GeV^(-2)with: Lambda = (740 +/- 74) MeVWithin the errors this result is consistent with the result of the Lepton-G experiment, the NA60 experiment, and the SND experiment. Furthermore the result agrees within the errors with the theoretical prediction of.In the investigation of the pion-Dalitz analysis no deviation from the QED-pre-diction was found. In the case of the omega-Dalitz decay a from factor could not be determined because of limited statistics.The determined branching ratios are: BR_Dalitz = (6.18 +/- 0.65) 10^(-3) BR_Eta->Pi+Pi-Pi0 = (22.9 +/- 1.7)% BR_Omega->GammaPion = (10.2 +/- 1.4)%These results are consistent with the values in the Particle Data Booklet of the Particle Data Group. Furthermore the obtained cross sections for eta-production and for pion-eta-production are in agreement with the results of former publications.
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