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The analysis of pbar p reactions in flight has been started up to now from the JPC intermediate states(Standard Method).The problem with the Standard Method is,that additional Clebsch-Gordan Coefficients describing the coupling of the pbar p system with the JPC system are not taken correctly into account.The same is true for the kinematical factors(different for different beam-energies).They are important in the comparison of amplitudes at different p energies.Here,the whole reaction chain is described starting from the antiproton- and proton- helicity states, avoiding the above mentioned complications.That is done for the pbarp→ωπ0, ω→π0γ reaction, but can be easily expanded to more general cases. A comparison of the results with the Standard Method is performed showing that the Standard Method does not reproduce the correct sign of the amplitudes. Also the spin density matrix of the omega is discussed and the determination of its elemen ts using different methods is outlined.