Production mechanism of ?0 and f mesons in πN→π+π?N reactions

The production of ?⁰ and f mesons in πN→π⁺π^?N reactions in the momentum range 4 to 17 GeV/c is investigated in a model-independent way by imposing in full the positivity of the density matrix. The results so obtained are used in order to determine the effective Regge trajectories for unnatural and natural parity exchanges and are compared to results obtained in different analyses.