Neutron hole states in Λ6Li, Λ7Li, Λ9Be and Λ12C hypernuclei

Neutron hole states in the 1s shell have been studied in the n(K−, π−)Λ strangeness-exchange reaction on 6Li, 7Li, 9Be, and 12C targets at the CERN Proton Synchrotron. The excitation energy and the width of the states as well as the differential cross section have been determined. The clear similarity with the 1s proton hole states observed in (p, 2p) reactions indicates that the presence of the Λ-particle can be taken into account within the weak-coupling model. In this way the (K−, π−) reaction can be used for the study of Λ -states as well as for the investigation of neutron hole states produced at very low momentum transfer.