Formation of S=-2 hypernuclei

Discussion is given about new data of Ξ-.12C hyperatomic and/or hypernuclear systems from the emulsion-counter hybrid experiment at KEK. There is a possibility of the first reliable observation on the Ξ-hypernucleus. The branching ratio of the 4ΛΛH formation is obtained to be a high value 37% if a Ξ- hyperon is absorped from atomic s orbit. But it reduces to about 3% if the absorption occurs at the 2p orbit. The breakup of an alpha cluster profits the formation of double-Λ hypernuclei. A stopped Ξ- on 9Be can effectively produce various light double-Λ hypernuclei. Discrete pion spectra from the weak decay of the products can provide a way of mass spectroscopy of double-Λ hypernuclei. (orig.)