The $\Theta^+$ Pentaquark is a Very narrow $\Gamma \approx 1$ MeV KN Resonance. Why do some experiments see it and others do not? The lowest quark configuration that can describe it is exotic $uudd \bar s$. Why have no exotics been seen before? Is this the beginning of a new spectroscopy? Can it help toteach us about How QCD makes hadrons from quarks and gluons?
The theory of pentaquarks
Why the Theta+ is seen in some experiments and not in others - a possible explanation
Do experiments suggest a hierarchy problem?
