A MYSTERIOUS particle that doesn’t seem to fit any existing theory of matter has physicists puzzled. Dubbed X, it may be the first in a new family of subatomic particles that are bound together a bit like molecules.
Many subatomic particles are made up of quarks, which come in six flavours: up, down, strange, charm, bottom and top. The quarks can combine into baryons, such as protons and neutrons, which consist of three quarks each, or mesons, made of a quark and an antiquark.
Physicists at the KEK collider in Tsukuba, Japan, were trying to make a particle which contains…
