Towards a new paradigm in hadron spectroscopy
Understanding the hadron spectrum is one of the premier challenges in particle physics. For a long time, the quark model has served as an ordering scheme and brought systematics into the hadron zoo. However, many new hadrons that were observed since 2003 do not conform with quark model expectations. Here, we demonstrate that if the lightest scalar, the Ds0*(2317), and axial-vector, the Ds1(2460), states are assumed to owe their existence to the nonperturbative dynamics of Goldstone-Boson scattering off D and D* mesons, various puzzles in the spectrum of the charm mesons find a natural resolution. Most importantly the ordering of the lightest strange and nonstrange scalars becomes natural. Furthermore it is demonstrated that the well constrained amplitudes for Goldstone-Boson scattering off charm mesons are fully consistent with recent high quality data on the B−→ D+π−π− final states provided by the LHCb experiment at CERN. This implies that the lowest quark-model positive-parity charm mesons, together with their bottom cousins, do not form the ground-state multiplet. In a broader view, the hadron spectrum must be viewed as more than a collection of quark model states.