Production of twin Λ-hypernuclei from Ξ- hyperon capture at rest

A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Xi (-) hyperon capture at rest with the expectation of ten times larger statistics than previous experiments. We have analyzed 5% of the total emulsion and found one twin-hypernuclei event involving the emission of two single-Lambda hypernuclei and a nuclear fragment from a Ehyperon stopping point. The event is interpreted as the decay of a Xi (-) + N-14 atomic system to He-5(Lambda) + He-5(Lambda) + He-4 + neutron. The species of the Xi (-)-atom and the fragmentation products are uniquely identified for the first time for twin-hypernuclei events. Combined with the results from a past hybrid-emulsion experiment, one double-Lambda hypernucleus and three twin-hypernuclei events have been found from Xi (-) captures on light emulsion nuclei. The ratio of the detected rate of double-Lambda hypernuclei to that of twin-hypernuclei is compared with theoretical estimates. (C) 2001 Elsevier Science B.V. All rights reserved.