When hadrons become unstable: a novel type of non-analyticity in chiral extrapolations

Understand

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.