HYPERFRAGMENT

also called Hypernucleus, atomic nucleus containing a lambda-zero (L0) hyperon (subatomic particle more massive than a proton or neutron). A hydrogen hypernucleus (4H), for example, consists of a lambda particle, a proton, and two neutrons. Study of this and similar short-lived hyperfragments, discovered (1953) by M. Danysz and J. Pniewski, gives information on nuclear structure, spin of the lambda-zero hyperon, and the nuclear force (or strong interaction) that binds the lambda particle to the protons and neutrons.