The quark model was formulated in 1964 to classify mesons as bound states made of a
quark–antiquark pair, and baryons as bound states made of three quarks. For a long time all …

Quantum Chromodynamics, the theory of quarks and gluons, whose interactions can be
described by a local SU (3) gauge symmetry with charges called “color quantum numbers” …

A large number of experimental discoveries especially in the heavy quarkonium sector that
did not meet the expectations of the until then very successful quark model led to a …

The spectrum of hadrons is the manifestation of color confinement of quantum
chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003 …

In this review, we present the current state of the art of our understanding of the spectrum of
excited strongly interacting particles and discuss methods that allow for a systematic and …

A bstract In this third paper of a series dedicated to a dispersive treatment of the hadronic
light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate …

The existence and properties of the sigma meson have been controversial for almost six
decades, despite playing a central role in the spontaneous chiral symmetry of QCD or in the …

We discuss recent lattice data for the T cc (3875)+ state to stress, for the first time, a
potentially strong impact of left-hand cuts from the one-pion exchange on the pole extraction …

The vast majority of hadrons observed in nature are not stable under the strong interaction;
rather they are resonances whose existence is deduced from enhancements in the energy …

Physical states are characterised uniquely by their pole positions and the corresponding
residues. Accordingly, in those parameters also the nature of the states should be encoded …