Glueballs are an unusual, unconfirmed Standard Model prediction, suggesting bound states of gluons alone exist. We just found our first one.
A view from above of the BES III detector at the electron-positron collider in Beijing, China. Exotic particles have newly been detected here, including X, Y, and Z mesons which don't fit the normal scheme of a quark-antiquark combination. With the X(2370) particle, we may have detected the first glueball in history
At a fundamental level, the matter we know of is largely composed of quarks, like the up and down quarks, which make up protons and neutrons: the particles at the heart of every atom’s core. Quarks and gluons, operating under the strong force and the rules of quantum chromodynamics, make up all the known hadrons, baryons, and mesons in existence, providing us with a huge spectrum of particle states. But, in theory, there should be another kind of bound state never observed before: glueballs, which are quarkless composite particles made of bound gluons alone. At last, in 2024, we may have found our first one..
When it comes to the Standard Model of particle physics, most people incorrectly assume that it’s known, it’s correct, and that there are no more open questions about its validity. While the Standard Model has certainly withstood every challenge that’s been thrown at it by way of direct detection experiments, there are still a whole slew of questions that have yet to be answered. Although the matter that makes us up is composed of atoms, which are made of protons, neutrons, and electrons, and where the protons and neutrons are made up of three quarks apiece — all held together by gluons through the strong interaction — that’s not the only possible way to have bound states of matter.
In theory, at least according to quantum chromodynamics (our theory of the strong nuclear force), there should be multiple ways to make a bound state of quarks, antiquarks, and/or gluons alone. You can have baryons (with 3 quarks each) or anti-baryons (with 3 antiquarks each). You can have mesons (with a quark-antiquark pair). You can have exotic states like tetraquarks (2 quarks and 2 antiquarks), pentaquarks (4 quarks and 1 antiquark or 1 quark and 4 antiquarks), or hexaquarks (6 quarks, 3 quarks and 3 antiquarks, or 6 antiquarks), etc. Or, you can also have states made of gluons alone — with no valence quarks or antiquarks — known a glueballs. In a radical new paper just published in the journal Physical Review Letters, the BES III collaboration just announced that an exotic particle, previously identified as the X(2370), may indeed be the lightest glueball predicted by the Standard Model. Here’s the science of the claim, as well as what it all means.
International Research Conference on High Energy Physics and Computational Science
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