The Resolving Power of a Reaction

We describe a simple method to compute the Cramer-Rao limit of a high energy experiment, i.e., the smallest error with which a parameter can in principle be determined in a reaction. This precision remains a theoretical paradigm since it assumes perfect experimental conditions. Nevertheless, it is shown at hand of an example that for simple processes this asymptotic resolving power can be approached very closely. In all situations, the procedure is at least a useful test of what could and what cannot be measured by studying a particular reaction.