Speaker
Description
We address pion transitions involving heavy quarkonium and heavy exotic states in the Born-Oppenheimer effective field theory. Some of these states have a size similar or larger than typical hadronic scale. For these states the usual QCD multipole expansion breaks down and the transition form factors become unknown functions. To address this, we propose an interaction Lagrangian for pions and the QCD string that allows us to determine the long distance behavior of the form factors. As a by product, it also allows us to calculate the light quark mass dependence of the string tension. Applying this framework, we calculate several quarkonium-to-quarkonium and hybrid-to-quarkonium transitions, providing a phenomenological analysis of the most relevant ones.