Towards meson spectroscopy instead of bump hunting

In the present paper, a largely empirical yet very successful approach to meson spectroscopy is revisited, in which all the above phenomena can be accounted for non-perturbatively, with concrete examples of some enigmatic mesonic states described in detail. First, the X(4260) charmonium enhancement is argued to be a non-resonant structure resulting from depletion effects due to competing channels and resonances. Then, the X(3872) charmonium-like meson is described as a unitarised JPC=1++cc̄ state. Also, the unusual pattern of masses and widths of the open-charm axial-vector mesons D1(2420), D1(2430), Ds1(2536), and Ds1(2460) is shown to follow from highly non-perturbative coupled-channel and mixing effects. Finally, first indications of a very light scalar boson are presented, on the basis of published BABAR data.