Constraints on the absorptive scattering amplitude from positivity

Bounds on the absorptive part of scattering amplitude are determined for physical scattering angles using unitarity, the impact parameter representation, and the derivatives of the amplitude in the forward direction. The bounds are computed for experimental examples and are found to be tighter in cases considered than those obtained by previous methods. An improved lower bound on the derivatives of the amplitude for physical scattering angles is also derived. (Auth.)