Physicists with the Beijing Spectrometer III (BESIII) Collaboration have presented what independent experts describe as persuasive evidence for the existence of a glueball, a particle composed entirely of gluons.
Gluons are the force-carrying particles that bind quarks into protons and neutrons; a glueball would be a bound state of gluons interacting with themselves, a key prediction of quantum chromodynamics.
The candidate particle, known as X(2370), was first observed in 2011 during decays of the J/ψ meson, a process theorists consider a prime hunting ground for glueballs.
Over 13 years, the BESIII team analyzed nearly ten billion J/ψ decays produced at the Beijing Electron–Positron Collider II at the Institute of High Energy Physics.
In 2024, the collaboration determined that X(2370) has a spin-parity of 0⁻⁺, identifying it as a pseudoscalar particle consistent with the predicted properties of the lightest glueball.
Bruce Yabsley of the University of Sydney, who reviewed the results, said no single measurement is a smoking gun but the cumulative evidence built over decades is quite persuasive.
Ulrik Egede of Monash University, who attended the conference presentation in Natal, Brazil, described the evidence as quite convincing.
Confirming glueballs would provide direct evidence of gluon self-interaction and help explain how the strong force generates most of the mass of protons, since the constituent quarks account for only a small fraction of the proton's mass.
A particle made of force: physicists say they’ve found mysterious ‘glueball’
This is an independent summary. The complete reporting, supporting context and any primary documents remain with Nature.