The theory of the strong force, Quantum Chromodynamics (QCD), describes how the elementary constituents of nucleons (quarks and gluons) interact and build visible matter. After half a century of research, enormous progress has been made, concerning essentially the quark content of nuclear systems. However, very little is known about the impact of gluons, the carriers of the interaction itself, on the properties of nucleons, and of nuclei as well.
In order to study the very nature of the strong force, an Electron-Ion Collider (EIC) is planned within the next 5-10 years in the USA. This will be the first polarized electron-ion collider in the world, and will offer a unique opportunity to understand the role of gluons in strongly interacting systems. It will provide the kinematics to explore a new state of matter predicted by QCD (the color-glass condensate), in which gluons dominate, and hints of which have been observed in colliders such as HERA, RHIC, and the LHC. In addition, thanks to recent developments at electron-scattering facilities such as Jefferson Lab, the EIC will also allow to quantitatively understand the internal structure of nucleons and nuclei, and to explain how their macroscopic properties (such as their mass and spin) arise from the degrees of freedom of QCD.
This seminar will review the most pressing questions in our understanding of QCD and how an EIC will address them. The organization of the EIC users community around the world will be also outlined. Finally, the current status of the R&D on the detectors will be presented.
