Y. H. Iwata

Production of twin λ-hypernuclei from ξ- hyperon capture at rest

Abstract A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Ξ− 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-Λ hypernuclei and a nuclear fragment from a Ξ− hyperon stopping point. The event is interpreted as the decay of a Ξ − + 14 N atomic system to 5 Λ He + 5 Λ He + 4 He + neutron . The species of the Ξ−-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-Λ hypernucleus and three twin-hypernuclei events have been found from Ξ− captures on light emulsion nuclei. The ratio of the detected rate of double-Λ hypernuclei to that of twin-hypernuclei is compared with theoretical estimates.

Doubly strange nuclei by a hybrid-emulsion experiment E373 at KEK

A hybrid emulsion experiment E373 at KEK has been carried out to study doubly strange nuclear system. By the 8% data analysis of all, one twin single-Λ hypernuclei event and two events of double-Λ hypernucleus have been successfully detected. The twin single-Λ event is uniquely interpreted as Ⅺ−+14N→Λ5He+Λ5He+4He+n for the first time. In the first double-Λ hypernucleus event, “Demachi-Yanagi,” it is interpreted as Ⅺ−+12C→ΛΛ10Be* (or ΛΛ10Be*)+t. The second double-Λ hypernucleus event, “NAGARA,” shows a clearly recognized topology and the interpretation is unique as Ⅺ−+12C→ΛΛ6He+4He+t, ΛΛ6He→Λ5He+π−+p, Λ5He→p+d+2n etc. By the preliminary result of the ΛΛ6He, the attractive ΛΛ interaction has been confirmed with the ΔBΛΛ∼1 MeV.

Observation of double-hypernuclei and Λ-Λ interaction

Abstract A hybrid-emulsion experiment has been carried out at KEK-PS to study S = −2 nuclei. With the analysis of about 35% of total emulsion, we have successfully found three events of sequential weak decay of a double-hypernucleus. The results of these E373 events are summarized together with those of past experiments. The first experimental study of the branching ratios of weak decay modes of double-hypernuclei has been performed.

Study of double-strangeness nuclei with hybrid-emulsion method (KEK-PS E373)

Abstract An experiment to search for double-strangeness nuclei in nuclear emulsion is now being carried on as KEK-PS E373. Preliminary results of the data analysis for the K + spectrometer and the scintillating fiber detectors are presented. Status of the automatic track finding method for the emulsion is reported.