When hadrons become unstable: a novel type of non-analyticity in chiral   extrapolations
  Hadron masses show a specific dependence on the quark masses. Therefore, the variation of these masses can cause a resonance in a hadronic scattering amplitude to become a bound state. Consequently, the amplitude exhibits a non-analytic behavior at this transition. Crossed amplitudes, where the resonance can be exchanged in the t-channel, can be shown to exhibit the same phenomenon by s-->t analytic continuation. This entails possible kinks in lattice quark mass extrapolations needed to compute hadronic observables. 
F.-K. Guo, C. Hanhart, F. J. Llanes-Estrada, U.-G. Mei{\ss}ner
hep-lat hep-ph nucl-th