The Search for QCD Exotics
Particles predicted by the theory of quantum chromodynamics help explain why the fundamental building blocks of matter are impossible to isolate
Protons in the nuclei of atoms would fly apart were it not for the strong nuclear force. This force is carried by particles (called "gluons") just as the electromagnetic force is carried by particles (photons). Photons have no charge and cannot associate together; hence there are no atoms of light. But gluons carry a type of charge (so-called "color" charge) and so can clump together. The result of such an amalgamation is a glueball, a particle made up of nothing more than the force that holds nuclei together. Physicists have long sought experimental evidence for glueballs and for exotic combinations of glueballs and ordinary particles. The authors describe some of these past attempts and explain their own strategy for uncovering various exotic particles predicted by the theory of quantum chromodynamics (QCD).
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