We explore the phenomenology of, and models for, the $Z^{*}$ resonances, the lowest of which is now well established, and called the $\Theta .$ We provide an overview of three models which have been proposed to explain its existence and/or its small width, and point out other relevant predictions and potential problems, for each. The relation to what is known about KN scattering, including possible resonance signals in other channels, is also discussed.

• Received 11 December 2003

DOI:https://doi.org/10.1103/PhysRevD.69.094020