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 […]