According to the website of the Institute of High Energy Physics, Chinese Academy of Sciences, on August 6th, at the International High Energy Physics Conference held in Brazil, the BESIII experiment team from the Beijing Spherical Telescope announced that after 15 years of continuous research, they have established a complete chain of evidence for the existence of spherical particles, solving the mystery of the existence of spherical particles that has plagued the academic community for nearly half a century.
The atomic nucleus is composed of protons and neutrons, which in turn are made up of quarks. The strong interaction between quarks is mediated by gluons, just as the electromagnetic interaction is mediated by photons. However, the special feature of gluons is that they can attract each other, unlike photons. Therefore, it is possible for gluons to attract each other, resulting in a new type of particle—the gluon ball.
In the physics theory that describes strong interactions, known as quantum chromodynamics, gluons are a crucial prediction. They are the only particles made up of “force-carrying particles”. However, for half a century, gluons have not been found in experiments. This failure to detect gluons is one of the major scientific questions that remain unresolved in this physics theory.
Beijing National Laboratory Physics III Detector – Website of the Institute of High Energy Physics, Chinese Academy of Sciences
The Beijing Electron Pulse Collider is capable of producing a large number of J/psi particles, which were discovered by Mr. Dijstal. These particles decay into lighter particles immediately after being produced. Theoretically, the decay process of J/psi particles is very conducive to the formation of jets, making it one of the best ways to search for jets. Therefore, the experimental search for jets has been one of the primary physical goals of the Beijing Electron Pulse Collider over the past few decades.
In 2011, researchers working on the BESIII collaboration discovered a new particle X(2370) in the decay products of J/psi. It was suspected to be a glueball. After 13 years of effort, they were able to measure the spin and parity quantum numbers of X(2370) using 10 billion particles of J/psi in 2024. The mass of X(2370) matched the theoretical predictions of lattice quantum chromodynamics for glueballs with the same quantum numbers, marking a crucial step towards determining its true identity.
Recently, a research team led by Professor Jin Shan from Nanjing University and Researcher Huang Yanping from the Institute of High Energy Physics of the Chinese Academy of Sciences has made significant progress: they have discovered several new decay modes of the X(2370) particle, and for the first time, measured another key “identity characteristic” of this particle—its “flavor singlet” property.
The “flavor singlet” property is the most important characteristic of glue balls. Ordinary particles such as protons and neutrons contain quarks with different “flavors”, such as upper quarks, lower quarks, and strange quarks. However, glue balls are composed solely of gluons and do not contain flavor information, thus they belong to the “flavor singlet” state. Recent experimental results have successfully determined that X(2370) is in the “flavor singlet” state.
This means that after 15 years of continuous research, the BESIII experiment has established a complete chain of experimental evidence from mass, quantum numbers to the ‘flavor singlet state’. It confirms that the main component of X(2370) is indeed the gluon ball that physicists have been searching for for nearly half a century.
This is the clearest experimental result in the search for gluons in nearly half a century. It clearly confirms the significant theoretical prediction that "gluons can combine with each other to form new substances," and also demonstrates the unique advantages of the Beijing Electron-Positron Collider in studying strong interactions. This discovery not only provides a decisive confirmation for the theory of "quantum chromodynamics," but also indicates the existence of a new type of matter—matter composed entirely of "force."
Beijing Synchrotron Radiation Facility III is a large-scale particle physics detector operated at the Beijing Electron-Positron Collider. Its international collaborators consist of approximately 700 scientists from about 96 research institutions in 15 countries. The experiment focuses on precise physical research in the tau-charm energy range, achieving a series of world-leading results in fields such as hadron spectroscopy, charms physics, tau physics, and the search for new physics.
