Solution of the unitarity equation with overlapping left and right cuts: A tool for study of the <i>S</i>* and similar systems

Abstract

The partial-wave unitarity condition is complicated by the presence of overlapping left and right branch cuts when the lowest exchanged mass is small in comparison to the direct-channel mass. A coupled-channel ND−1 method for constructing unitary amplitudes with overlapping cuts is described. The study is motivated in part by the problem of analyzing the ππ−K̄system near the S* resonance.