Beijing, April 19 (Xinhua/Sun Zifa): Researchers from the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences announced on April 19th a significant discovery from the Beijing Spectrometer III experiment, a core research facility of the Beijing Electron Positron Collider. The latest finding reveals a resonance structure labeled as X(1880) with a mass of 1882 mega-electron volts (MeV), strongly suggesting the existence of proton-antiproton bound states.
This milestone in particle physics research was jointly accomplished by Dr. Fang Shuangshi from IHEP, doctoral candidate Chen Tong, and Associate Professor Qin Liqing from Guangxi Normal University, among other collaborators of the Beijing Spectrometer III project. The breakthrough has been highlighted in a recent publication in the prestigious international academic journal "Physical Review Letters" and simultaneously announced by the American Physical Society under the title "Evidence for a New Subatomic Particle."
The schematic diagram of the research findings. Institute of High Energy Physics, Chinese Academy of Sciences/Provided
The research team introduced that the proton is one of the basic particles that make up the atomic nucleus, while the antiproton is the antimatter counterpart of the proton, with the same mass but opposite charge. When protons and antiprotons meet, they annihilate each other, releasing tremendous energy. However, some theories predict that protons and antiprotons can also combine through strong interaction to form a short-lived state known as proton-antiproton bound state. Searching for such novel hadronic states is one of the important goals of high-energy physics experiments.
As early as 2013, the Beijing Spectrometer III experiment, while studying the decay process of the J/ψ particle into a photon and three pairs of positive and negative pions, first discovered a new resonance structure X(1840) in this process. Its mass is just near the mass threshold of proton-antiproton, but slightly below that threshold. In-depth studies of this resonance structure are crucial for understanding its properties.
Currently, the Beijing Spectrometer III experiment has collected 10 billion J/ψ decay events, which is 50 times the statistics of previous studies using data samples, laying a solid foundation for further research. Utilizing this data set, researchers have observed for the first time an anomalous structure on the mass spectrum. This structure is formed by the superposition of two resonance structures. In addition to X(1840) discovered in 2013, there exists a new resonance structure named X(1880), with a statistical significance exceeding 10 standard deviations.
The research team stated that the mass of this new resonance structure X(1880) is slightly heavier than the sum of a proton and an antiproton, resembling properties of proton-antiproton bound state, providing new experimental evidence for the existence of proton-antiproton bound state.
It is understood that in this study, the maintenance and offline software teams of the Beijing Spectrometer III detector, as well as the operation and maintenance team of the Beijing Positron-Electron Collider, have made important contributions to data collection and analysis. (End)
