Extraction of parameters from final state interactions

It is argued that final state enhancements in production reactions at large momentum transfers, such as pp -> K^+ Lambda p, are primarily sensitive to the position of a virtual bound state pole in the Lambda p system rather than the Lambda p scattering length and effective range. These arguments are supported by a study of the dispersion relation derived to describe such processes as a function of the cut-off energy. This shows that the position of the virtual bound state is independent of the cut-off energy.