  We prove a lower bound for the modulus of the amplitude for a two-body
process at large scattering angle. This is based on the interplay of the
analyticity of the amplitude and the positivity properties of its absorptive
part. The assumptions are minimal, namely those of local quantum field theory
(in the case when dispersion relations hold). In Appendix A, lower bounds for
the forward particle-particle and particle-antiparticle amplitudes are
obtained. This is of independent interest.
