Unitarity restrictions on meson-nucleon helicity-flip amplitudes and slope of the diffraction peak

The MacDowell-Martin bound on the slope parameter bsup(A) for the spinless case is generalized to the case of spin-0-spin-1/2 elastic scattering with parity conservation. The optimal answer for all energies is given as well as the simpler (slightly weaker) bound bsup(A)>=σsub(tot)sup(2)/36πσsub(el)[square root(1+9πσsub(el)/4k2σsub(tot)sup(2))+1]-1/4k2 (k = c.m. momentum). Here the superscript A refers to the absorbtive-part contribution. Unitary restrictions on the helicity-flip amplitude fsub(+-)sup(A)(t)/square root(-t) in terms of σsub(tot), σsub(el) and bsup(A)(s) are also given