Unitarity upper bound on the absorptive parts of elastic scattering amplitudes

Abstract

We derive a unitarity upper bound on the absorptive part A(s, t) of the elastic-scattering amplitude in the physical region. In the diffraction peak region the bound on A(s, t)/A(s, 0) is a function only of the parameter σ_tot²(−t)/4πσ_el. Assuming the diffraction scattering to be purely absorptive and spin independent we find the pp, p̅p, and π^±p data to lie a little below the theoretical upper bound. Further the experimental curve of X(t)/X(0) vs −4tX(0)/σ_el, where X(t)≡dσ/dt, seems "universal."