The Science and Status of the Electron Ion Collider: Understanding the Glue That Binds Us All
Despite many decades of investigations and tremendous progress both on experimental and theoretical front, many simple but important questions in QCD remain unanswered. For example, where does the proton’s spin come from? How are gluons and sea quarks distributed in transverse position and momentum space in the proton (or a neutron)? Does orbital motion of quarks and gluons contribute to the nucleon’s spin? What happens to those distributions once a proton is part of a larger nucleus? How do quarks, gluons and jets lose energy while passing through dense nuclear medium? How do they form colorless hadrons? Do the gluons in protons and nuclei at extremely high energy look the same or different? These and such questions are intimately connected to one of the most important but ill-understood phenomena in QCD: Confinement. They are all emergent phenomena resulting from non-linear color interactions present in QCD. We propose a high-energy, high-luminosity electron-nucleus and polarized electron-proton collider (called the Electron Ion Collider or the EIC) to answer the above questions. The EIC frontier accelerator facility was recommended by the US Nuclear Science Advisory Committee (NSAC) in 2015 as the next new facility to be built in the US. I will present the science and the status of the EIC project.