[7] Through the strong interaction, gluons bind quarks into groups according to quantum chromodynamics (QCD), forming hadrons such as protons and neutrons.

The stable strongly interacting particles, including hadrons like the proton or the neutron, are observed to be "colorless".

It is also impossible to add them to make rr, gg, or bb[12] the forbidden singlet state.

Quarks are introduced as spinors in Nf flavors, each in the fundamental representation (triplet, denoted 3) of the color gauge group, SU(3).

For a general gauge group, the number of force-carriers, like photons or gluons, is always equal to the dimension of the adjoint representation.

There is no known a priori reason for one group to be preferred over the other, but as discussed above, the experimental evidence supports SU(3).

These gluon–gluon interactions constrain color fields to string-like objects called "flux tubes", which exert constant force when stretched.

At a large enough distance, it becomes energetically more favorable to pull a quark–antiquark pair out of the vacuum rather than increase the length of the flux tube.

In summer 1979, at higher energies at the electron-positron collider PETRA (DESY), again three-jet topologies were observed, now clearly visible and interpreted as qq gluon bremsstrahlung, by TASSO,[16] MARK-J[17] and PLUTO experiments[18] (later in 1980 also by JADE[19]).

Deconfinement was claimed in 2000 at CERN SPS[27] in heavy-ion collisions, and it implies a new state of matter: quark–gluon plasma, less interactive than in the nucleus, almost as in a liquid.

It was found at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven in the years 2004–2010 by four contemporaneous experiments.

[28] A quark–gluon plasma state has been confirmed at the CERN Large Hadron Collider (LHC) by the three experiments ALICE, ATLAS and CMS in 2010.

The Virginia lab was competing with another facility – Brookhaven National Laboratory, on Long Island, New York – for funds to build a new electron-ion collider.

[30] In December 2019, the US Department of Energy selected the Brookhaven National Laboratory to host the electron-ion collider.