Baryon resonances from chiral coupled-channel dynamics

Abstract

We discuss the formation of s- and d-wave baryon resonances as predicted by the chiral SU(3) symmetry of QCD. Based on the leading order term of the chiral Lagrangian a rich spectrum of molecules is generated, owing to final-state interactions. The spectrum of s- and d-wave baryon states with zero and non-zero charm is remarkably consistent with the empirical pattern. In particular, the recently announced Sigma_c(2800) of the BELLE collaboration is reproduced with realistic mass and width parameters. Similarly, the d-wave states Lambda_c(2625) and Xi_c(2815) are explained naturally to be chiral excitations of J^P=3/2^+ states. In the open-charm sector exotic multiplet structures are predicted. These findings support a radical conjecture: meson and baryon resonances that do not belong to the large-N_c ground state of QCD should be viewed as hadronic molecular states