K-matrix formalism and the quasi-two-body phase space factor in the isobar model

We discuss the generalization of the results of the coupled-channelK-matrix formalism as applied to scattering of stable particles to the case which involves isobars. In the process, we develop the phase-space integral for the quasi-two-body channel and show that its upper limit is ∞ in agreement with the general principles of analytic continuation of a partial-wave amplitude. In the past, the validity of this upper limit for the integral has not been fully clear.