Unitary parametrization of three-body observables

The three-particle unitarity relations are solved explicitly in order to derive a general representation for the measurable three-body amplitudes. The representation is characterized by a well-defined set of real parameters which are the equivalent of a phase-shift analysis for the three-body problem. The resulting parametrization is suitable for both the data analysis of three-particle final states, and as a starting point for a three-body phenomenology.