Can the top quark, the short-lived particle of all, bind with anything else? Yes it can! New results at the LHC demonstrate toponium exists.
Some particles just seem destined to be alone. Among atoms, helium and the other noble gases are famous for ignoring other atoms, displaying an energetics-based preference for remaining as isolated atoms over binding with any other atom, regardless of species. Among the fundamental particles, neutrinos (and antineutrinos) don’t appear to form any bound states, as they’re uncharged under both the strong nuclear and the electromagnetic force: the primary forces that bind particles together. The W-and-Z bosons are too short-lived to form bound states, as is the Higgs boson. But among particles with either an electric charge or a color charge (or both), there’s only one particle that was presumed to always remain in isolation: the top quark.
Of all the known fundamental particles, the top quark has both the greatest rest mass (at a little over 172 GeV/c²) and the shortest lifetime (at half a yoctosecond, or ~5 × 10^-25 s). The strong nuclear force — the force that binds quarks together into bound states like baryons and mesons — is an incredibly short-range force, but even “short-range” means…
