COST Action project on hadron physics

The goal of hadron physics is to understand the fundamental structure and dynamics of hadrons. Hadrons are bound objects confined by the strong interaction, and Quantum Chromodynamics (QCD) is the gauge theory describing it. Yet, many of its features are difficult to explain quantitatively, since the strong coupling becomes large in the energy regime where quarks form hadrons. Therefore, methods based on perturbative QCD are of limited use. Instead we rely on phenomenological models and lattice QCD that however need experimental data for input or benchmarking. The “Structure and spectroscopy of hadrons research project” (SHARP) will provide a new platform for addressing this problem.

Hadron physics consists of two main branches: structure and spectroscopy. Hadron structure encompasses the spatial and momentum distributions of quarks and gluons. The proton, the most stable composite building block of matter, has been a main focus of study. Its properties are described by universal theoretical quantities, like parton distribution functions and generalized parton distributions, but they require experimental validation. The selection of the most suitable observables for this purpose is a topic of debate. Hadron spectroscopy predicts a vast spectrum of bound states, including exotic mesons, tetraquarks, hadronic molecules, and glueballs. However, many of these are difficult to identify unambiguously. Increased collaborative efforts between experimental and theory communities are imperative to understand the observed spectra and enter uncharted hadronic territories.

ECT*’s permanent researcher Daniele Binosi will help SHARP establish a strong interconnection within the hadron physics community, whose common focus is to understand how elementary quarks and gluons give rise to the complex visible matter of the universe.