Duality, Meson Trajectories and Remarks on the Regge-Pole Model for;r0 (r;) Photoproduction

In the description of photo~reactions on the basis of the Argonne Regge cut model, it is pointed out that (i) the effect due to the m trajectory plays a role of the primitive Regge amplitude in the r+ p~n°+ p reaction and (ii) as the primitive-Regge amplitude for the r+P~"'J+P reaction, it is not appropriate to consider the p- or m-exchange amplitude whose magnitude turns out to be zero at about t =-0.5 (GeV /c)2, and the Regge amplitude due to a meson trajectory with unnatural parity can be regarded as one of the candidates. More-over, a possible degeneracy pattern for the unnatural parity trajectories is suggested