Nucleon, the basic building block of the Universe

"The visible Universe consists of electrons and nucleons. While the electron is known as one of fundamental particles, i.e., a member of the leptons, the nucleon has further substructures, consisting of quarks and gluons. These quarks and gluons are the degrees of freedom in quantum chromodynamics (QCD). However, it is still mathematically formidable to solve QCD in low-energy regions, in which nonperturbative features of QCD such as the spontaneous breakdown of chiral symmetry and the quark confinement play essential roles in describing properties and productions of hadrons. Based on these two characteristics, a great deal of effective approaches and methods has been developed well over decades, which has revealed what the nucleon is and how it looks like. Moreover, novel experimental techniques have unveiled the structure and properties of the nucleon and related excited hadrons.


In the present colloquium, we will review modern ideas in the context of QCD and the present status of the structure of the nucleon theoretically as well as experimentally. In addition, we will also introduce a cutting edge of modern nuclear and hadronic physics in layman’s terms. "