What is the nature of the I G J P =0+0+ K10K10 threshold enhancement?

The I G J P =0+0+ threshold enhancement in the K10K10system has been variously interpreted in terms of a complex scattering length, and in terms of a resonant state called the S*. Despite many experiments, it is presently impossible to objectively decide between these two hypotheses. The poor consistency of the data supporting the resonance interpretation is demonstrated by examining the results of the resonance parametrizations. The weighted average from all such experiments is M0=(1062±5) MeV/c2, Γ0=(97±11) MeV/c2, with χ2 probabilities of 1.4% and 0.1%, respectively. Thus, it appears likely that either the quoted errors are considerably underestimated or that the results of several experiments are incorrect, or perhaps both. In addition, the possible existence of energy-dependent interference effects cannot be excluded.