Σ Hypernuclei

We consider the possibility of forming doubly strange Ψ hypernuclei via the (K-, K) reactions on various nuclear targets. Because of the high momentum transfer involved, even at 00, the formation of high spin states is strongly favored. The available experimental information on the elementary processes K-p → K+Ψ- or K0Ψ0 is reviewed, leading to the determination of an optimum incident K- momentum of about 1.9 GeV/c for the forward formation of discrete Ψ hypernuclear states. The cross section for the process ΨN → ΛΛ, responsible for the damping width of Ψ states in nuclei, is estimated theoretically and the very limited experimental data are also reviewed. The resulting Ψ hypernuclear widths are of order 5 MeV. Emulsion data which have been interpreted as due to the existence of ΛΛ and Ψ- hypernuclei are discussed and used to obtain an approximate Ψ nuclear well-depth of 21--24 MeV. For this range of values, spectra of single particle Ψ- states are obtained, and calculated angular distributions for the formation of simple Ψ- particle--proton hole states in 4He, 12C and 28Si targets are presented. The peak 00 lab cross section at P/sub lab/ = 1.9 GeV/c for such states ranges from tens of nb/sr to about 1 μb/sr. We briefly mention other methods for forming Ψ hypernuclei, such as the three body reaction K- → KπΨ (K/sup em-dash/p → K+K0Ω- for Ω- hypernuclei)