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” …

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 …

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 …

We review the structure of Roy–Steiner equations for pion–nucleon scattering, the solution
for the partial waves of the t-channel process π π→ N ̄ N, as well as the high-accuracy …

We highlight the progress, current status, and open challenges of QCD-driven physics, in
theory and in experiment. We discuss how the strong interaction is intimately connected to a …

Calculations within QCD (lattice and sum rules) find the lightest glueball to be a scalar with
mass in the range of about 1000–1700 MeV. Several phenomenological investigations are …

A bstract Estimating the contribution from axial-vector intermediate states to hadronic light-by-
light scattering requires input on their transition form factors (TFFs). Due to the L andau–Y …

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 …

We consider the contribution of scalar resonances to hadronic light-by-light scattering in the
anomalous magnetic moment of the muon. While the f 0 (500) has already been addressed …

The last two decades have witnessed the discovery of a myriad of new and unexpected
hadrons. The future holds more surprises for us, thanks to new-generation experiments …