> After almost two decades of searching, a team of physicists in China says it has observed strong evidence of a mysterious particle called a glueball, which is made entirely of force-carrying particles. > ... The discovery of glueballs would provide direct evidence that gluons can interact with themselves, researchers say. This is a key prediction of quantum chromodynamics
> "quantum chromodynamics"
I had to google it: "the study of the strong interaction between quarks mediated by gluons"
It’s the theory of colour charge essentially, counterpart to electrodynamics. Quarks have colour, rather than electrical charge. Mediating particle is the gluon, analogous to (but entirely different from) the photon