Amazing stuff!
"... Now, using a particle collider in Beijing, researchers say they have effectively proved the existence of such a “glueball.” [subatomic particle made up of gluons]
the researchers argue that a particle called X(2370), which they produced by smashing electrons into positrons at high energies, has the properties expected of a glueball. ..."
"At the International Conference on High Energy Physics held in Brazil, the BESIII Collaboration at the Beijing Electron Positron Collider announced in a special plenary report that after fifteen years of sustained research, the BESIII Collaboration identified that the dominant constituent of the X(2370) is a pseudoscalar glueball with spin-parity quantum numbers of 0⁻⁺.
The strong interaction force tightly binds the quarks inside protons and neutrons. Its mediator is called the gluon, just as the photon mediates the electromagnetic interaction. Notably, however, gluons can attract each other and form an entirely new particle ¾ a bound state called glueball. The glueball is an important prediction of quantum chromodynamics, the theory that describes the strong interaction, and is also the only type of particle in nature composed entirely of force mediators; no particle of this kind has ever been observed experimentally, and its existence constitutes a crucial test of quantum chromodynamics. ...
The BESIII Collaboration discovered a new particle in J/ψ decays, called the X(2370), in 2011.
Following another 13 years of work, the Collaboration used a much larger sample of 10 billion J/ψ particles in 2024 to determine for the first time its spin and parity quantum numbers to be 0⁻⁺. Its mass and quantum numbers are in complete agreement with lattice-quantum-chromodynamics prediction for a pseudoscalar glueball (whose spin and parity is 0⁻⁺), marking a crucial step toward establishing its true identity.
Recently, the ... discovered several new decay modes of the X(2370) and, in particular, determined for the first time its “flavor-singlet” nature, which is the most important characteristic of a glueball.
This series of BESIII studies established a complete chain of experimental evidence: a pseudoscalar-glueball component must dominate the X(2370).
This is the clearest experimental result from nearly fifty years of searches for glueballs, verifying the major theoretical prediction that gluons can bind together to form a new type of matter. This result demonstrated unique advantages of the Beijing Electron Positron Collider in studies of strong interactions. ..."
Abstract (This a short 10 pages paper, oddly using the last four pages to list all names of involved researchers and their affiliation)
BESIII Experiment Identifies X(2370) as a Glueball Dominated Particle (original news release)
Lightest 0−+ Glueball as Dominant Constituent of X(2370) (preprint, open access)
Figure: BESIII
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