Abstract
The well-known soft-pion theorems for pion-baryon scattering are combined with finite-energy sum rules to (a) test the usefulness of given models of the absorptive amplitude, A+ νB; and (b) to gainn new information about the Regge exchanges. Assuming Regge terms only at intermediate and high energies ( W > 2100 MeV), and resonances at low energies, the πN sum rules predict combinations of Regge parameters in agreement with those from high-energy fits. In πΣ, πΛ scattering, the following results are obtained independently of the unknown gΣΣπ, gΣΛπcouplings: that I t = 2 exchange Regge terms must be very small; that the rho trajectory couples approximately universally to Σ; and that if P is an SU(3) singlet, then the P′ must couple to ( 1 2 +) baryons as a mixture of both singlet and octet. We also note the difficulty of saturating the πΣ Adler-Weisberger relation, unless the sum of couplings g ΣΛπ 2 + g ΣΣπ 2 is appreciably greater then the values expected from SU(3).
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