Backward meson-baryon scattering and geometrical properties of baryonic exchanges

On the basis of the “b universality” hypothesis, Regge behaviour and SU(3) symmetry, we discuss processes of the type $\text{0?}\text{1+}\text{2}\text{→ 0?}\text{1+}\text{2}$ at backward angles when significant data are available. Related annihilation processes by line-reversal are also studied and duality constraints are taken into account. On the whole a satisfactory scheme seems to emerge.