CA24159 - Structure and spectroscopy of hadrons research project (SHARP)

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 theory describing it. Yet, many of its features are difficult to explain from first principles, since the strong coupling becomes large in the energy regime where quarks form hadrons. Therefore, methods based on perturbative QCD are of limited applicability. Instead we rely on effective field theory, phenomenological models and lattice QCD that however need experimental data for input or validation. SHARP will provide a new platform for addressing this.

Hadron physics focuses on two key domains: internal structure and spectroscopy. Hadron structure involves 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 quantities, like the parton distribution functions and the generalised parton distributions, that require experimental validation. The selection of 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 experiment and theory are imperative to understand the observed spectra and enter uncharted hadronic territories.

SHARP will 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.