Title: Triangle singularities: a new tool for progress in Hadron Physics

Abstract:  Triangle singularities (TS) stem from mechanisms involving a Feynman diagram with a loop with three intermediate particles when they can be placed simultaneously on shell, are parallel and the mechanism can occur at the classical level (Coleman Norton theorem).  They were introduced by Landau in the 60’s, but no experimental examples were found at that time. The vast present phenomenology gives many examples of their presence.  In the talk we  show that several “resonances” cataloged in the PDG are not dynamical states but the consequence of a triangle singularity. We also show some examples of reactions where the TS appear and predictions for reactions where some suppressed production channels are drastically enhanced due to a TS.