Structure of Heavy Λ hypernuclei with a high-resolution magnetic spectrometer

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We have investigated the roduction, structure, and decay of Λ hypemuclei by using a high-resolution magnetic spectromerer. As for the production of hypermuclei, we used a new reaction of (π^-,Κ^+) rather than usually used (π^+,Κ^+) reactions. In this reaction,we cousk preduce neutron-rich Λ hypemuclei through the duble-charge exchange reaction. The result suggests the importance of virtual production og Σ hyperon in this reaction. We also invesitated real Σ production in a quasifree reaction to obtain the information of the Σ-Nucleus potentials in medum-heaby nuclei. The structure of a Λ hypemucleus with baryon uumber 89 was studied in detail. The energy levels of the ground state and excited states suggest that a Λ hyperon in the heavy hypernucleus has an effective mass of about 70% of the free Λ mass. In addition, the potential depth ovtained was 1-MeV deeper than so-far believed. In the non-mesonic weak decays of hypermuclei, we have succeeded to measure neutrons in high statistics with low backgrounds for the first time. The energy spectra of neutrons were nexpectedly smooth, which suggests the reaction mechanism of the non-mesonic weak decay should be reconsidered.For the extension of these invesigations, we have considered new hypermuclear experimental programs at the J-PARC which is now under construction. We have proposed several new experiments to the J-PARC.