|Budget Amount *help
¥1,500,000 (Direct Cost : ¥1,500,000)
Fiscal Year 1996 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1995 : ¥900,000 (Direct Cost : ¥900,000)
Recently, much interest is taken in double-strangeness states (XI hypernuclei, XI^- atoms and double-LAMBDA hypernuclei etc.) and interactions of elementary processes of LAMBDALAMBDA and XIN.Tne aim of our study was to investigate productions and structures of double-strangeness states, and transition processes due to strong interactions. In the KEK-E176 experiment with use of the hybrid technique of emulsion and counter, they observed the many XI^--stop events in emulsion after (K^-, K^+) reactions. Then, there were found one event of producing a double-LAMBDA nucleus and three events of simultaneous emissions of two single-LAMBDA hypernuclei. These events are considered that the XI^- trapped in an atomic orbit is absorbed into the nucleus, and the two LAMBDA produced by the XI^-p-LAMBDALAMBDA conversion stick to the nucleus.
On the other hand, we proposed the new idea of observing double-LAMBDA hypernuclei more efficiently : The XI^- particle produced predominantly in the quasi-free r
egion is absorbed into the target nucleus through the slowdown process due to the rescattering with a nucleon, and the XI^-p-LAMBDALAMBDA conversion in the nucleus leads to the double-LAMBDA sticking intermediate state (double-LAMBDA compound nucleus) and the following frag-mentation into double-LAMBDA products. Then, produced double-LAMBDA hypernuclei can be confirmed by detecting successive pions from their weak decays.
On the basis of the eikonal approximation we estimated the amount of double-LAMBDA sticking via tile slowdown process of quasi-freely produced XI particle. The fragmentation of the formed doublel-LAMBDA cormpound nucleus, treated with a statistical model, leads to several particular double-LAMBDA hypernuclei with high prob-abilities. In the case of the ^9Be target, especially, the number of breaking-up channels is small, and the production probability of ^5_<BDALAMBDA> is distinctively large. This feature gives a suitable and feasible condition of experiment with this target. Thus, the scenario of producing more double-LAMBDA hypernuclei through the slowdown of quasi-free XI^- was confirmed on the quantitative basis. Now a new experiment (E906) is in progress at BNL-AGS to detect double-LAMBDA hypernuclei by observing characteristic pi^- mesonic decays at (K^-, K^+) reaction points. The major results of out study were reflected in their proposal.
(2)捕獲されたΞ^-は核内陽子と反応して2個のΛに転換し、"double-Λ compound nucleus"が形成され、