Emergent phenomena and partonic structure in hadrons

TL;DR

This paper discusses how emergent phenomena like confinement and dynamical chiral symmetry breaking shape the partonic structure of hadrons, linking fundamental QCD mechanisms to observable properties and mass generation.

Contribution

It highlights the connection between emergent phenomena and the partonic structure of hadrons, emphasizing empirical avenues to verify these QCD effects.

Findings

Gluon and quark masses are large in the infrared, indicating confinement.

DCSB leads to a dressed-quark mass, explaining most visible mass.

Hadronic observables reflect confinement and DCSB effects.

Abstract

Modern facilities are poised to tackle fundamental questions within the Standard Model, aiming to reveal the nature of confinement, its relationship to dynamical chiral symmetry breaking (DCSB) - the origin of visible mass - and the connection between these two, key emergent phenomena. There is strong evidence to suggest that they are intimately connected with the appearance of momentum-dependent masses for gluons and quarks in QCD, which are large in the infrared: $m_g \sim 500\,$MeV and $M_q\sim 350\,$MeV. DCSB, expressed in the dynamical generation of a dressed-quark mass, has an enormous variety of verifiable consequences, including an enigmatic result that the properties of the (almost) massless pion are the cleanest expression of the mechanism which is responsible for almost all the visible mass in the Universe. This contribution explains that these emergent phenomena are expressed with particular force in the partonic structure of hadrons, e.g. in valence-quark parton distribution amplitudes and functions, and, consequently, in numerous hadronic observables, so that we are now in a position to exhibit the consequences of confinement and DCSB in a wide range of hadron observables, opening the way to empirical verification of their expression in the Standard Model.