Phys.org July 1, 2020
Researchers at CERN led by UK scientists found the new tetraquark using the particle-hunting technique of looking for an excess of collision events called bumps, over a smooth background of events. The bump has a statistical significance of more than five standard deviations, the usual threshold for claiming the discovery of a new particle, and it corresponds to a mass at which particles composed of four charm quarks are predicted to exist. As with previous tetraquark discoveries, it is not completely clear whether the new particle is a “true tetraquark”, that is, a system of four quarks tightly bound together, or a pair of two-quark particles weakly bound in a molecule-like structure. Either way, the new tetraquark will help theorists test models of quantum chromodynamics, the theory of the strong interaction…read more. Open Access TECHNICAL ARTICLE
…Four components are present as each projection consists of signal and background J/ψJ/ψ candidates… Credit: CERN