Nature has four fundamental forces: gravity, the weak force (responsible for radioactivity), electromagnetism, and the strong force. The strong force is responsible for keeping the protons and neutrons together in the nuclei of atoms.
The theory describing the strong interaction between two particles is called quantum chromodynamics (QCD). In QCD, the strong force is carried by gluons — just like how the electromagnetic force is carried by photons. But unlike photons, gluons carry a kind of charge that allows gluons to be attracted to each other. And QCD says they can come together to form composite particles called glueballs.
In new research, scientists have taken a big step closer to showing glueballs exist. The team used data from the BESIII experiment in Beijing to uncover them. This is easier said than done because when a glueball appears in a particle physics experiment, it will be very short-lived and quickly decay into lighter particles in a way that is hard to distinguish from some other particles.
Scientists had first observed a candidate glueball called X(2370) in BESIII data in 2011. Its mass seemed consistent with a glueball. They also estimated some of its properties based on the decays of a particle called the J/ψ meson. The new data buttresses the odds that X(2370) is indeed a glueball by revealing more properties glueballs possess.
Thus, BESIII has assembled the strongest case to date that X(2370) has a dominant glueball component, potentially providing the first evidence for a form of matter made just from the carriers of a fundamental force.
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