Progress Report in Hypernuclear Physics

摘要

New developments in lambda -hypernuclear structure are reported in light of recent studies of the (K exp - ,pi exp - ) reaction at BNL, particularly on exp 13 C. The smallness of the lambda -nucleus spin-orbit potential and the appreciable degree of coherence involved in the forward /sup A/Z(K exp - ,pi exp - )/sup A//sub lambda/Z reaction are discussed, suggesting a generalization in the former case and a breakdown in the latter case for sigma hypernuclei. Specifically, it is argued that the coherence generally expected in low momentum transfer production of sigma hypernuclei may substantially deteriorate, because a strong spin and isospin dependence of the sigma N interaction are likely to lead to a considerable energy spread of the (K exp - ,pi exp - ) strength with occasionally large energy shifts for some states. Finally, several observations are made on widths of sigma -hypernuclear states, both from a theoretical point of view as well as in connection with the relatively narrow levels discovered first in CERN for /sub sigma / exp 9 Be and recently at BNL for /sub sigma / exp 6 H. Further implications of the selectivity to the spin-isospin level structure argued for sigma -hypernuclear widths are suggested in exp 3 He and exp 4 He.