The Belle Experiment at KEK laboratory in Japan has discovered two unexpected new types of hadrons. Hadrons are composite particles made up of quarks, the smallest known components of matter.
These new particles are thought to contain at least four quarks, making them exotic hadrons -- hadrons that do not fit the quark model originally developed in 1961.
The B Factory experiment at KEK previously discovered exotic hadrons containing charm quarks. With this new finding, the Belle experiment has identified the first of this type of exotic hadrons discovered to contain bottom quarks, the second-heaviest type of quarks among the six known types of quarks. The particles, termed Zb, contain both one bottom quark and one anti-bottom quark.
Read more in a press release from KEK laboratory.