Production of Light Single-LAMBDA and Double-LAMBDA Hypernuclei in XI^- Atomic Capture Reaction

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1) The production rates per XI for the LAMBDALAMBDA^<12>Be+p, LAMBDALAMBDA^<12>B+n, LAMBDALAMBDA^<11>Be+d, LAMBDALAMBDA^9Li+alpha, LAMBDALAMBDA^<10>Be+t, LAMBDALAMBDA^6He+^7Li, LAMBDALAMBDA^5He+^8Be, LAMBDA^8Li+LAMBDA^5He, LAMBDA^9Be+LAMBDA^4H and LAMBDA^<12>B+LAMBDA channels (including their excited channels) via the ^<12>C-XI^- atomic states have investigated within the fame of the doorway double-LAMBDA hypernuclear picture (direct reaction picture). We found that in the stopped XI^- reaction the excited double-LAMBDA hypernuclear states for LAMBDALAMBDA^<12>B,LAMBDALAMBDA^<12>Be and LAMBDALAMBDA^<11>Be are greatly produced via the resonant states of the final double-LAMBDA hypernuclear channels. The following sequential process is possible ; (^<12>C,XI^-) atom * LAMBDALAMBDA^<12>B^<**>+n * LAMBDALAMBDA^<11>Be+p+n or LAMBDALAMBDA^<11>B+n+n. This process is similar to the sequential process for LAMBDALAMBDA^<13>B production observed in the KEK-E176 experiment, (^<14>N,XI^-) atom ** LA … More MBDALAMBDA^<14>C^*+n * LAMBDALAMBDA^<13>B+p+n. The calculated double-LAMBDA sticking probability is about 5 %, which is in correspondence to the experimental data.2) The excitation functions of the ^9Be(K^-, K^+)XI^9He reaction at P_K=1.6 GeV/c and rheta=0ﾟwere ecaluated with the Woods-Saxon type (VO=-24 and -16 MeV) and folding-type (YNG-ND No.1 and No.2) XI^--^8Linuclear potentials. The XI^--^8Li nuclear potentials except the folding potential (YNG-ND No.1) gives a broad peak at the XI bound-state region, which cross section is 0.02 - 0.08mub (0.2nb for YNG-ND No.1). The peak consists of the three component coming from the three XI^9He bound states. We estimated the production cross section of XI^9He (g.s.) * LAMBDALAMBDA^8He + n for the XI^--^8Li nuclear potentials. The calculated production rates were about 0.4%, and then, the production cross sections were 0.03 - 0.1 nb (0.3 pb) for the XI^--^8Li nuclear potentials except the folding potential (YNG-ND No.1)3) A selection rule for fragmentations of doorway s-hole states in light nuclei was given. In the two-body fragmentation process of the doorway s-hole states in light nuclei, smaller fragments than the alpha particle (p, n, d, t, and 3He) are allowed, while the fragments such as the alpha particle and the larger particles are forbidden, in spite of the fact that the Q value for the alpha fragment is similar to or even larger than those for the p, n, and d fragments. The selection rule comes from the spatial symmetry of the dooray s-hole states, The spectroscopic factors and partial widths for the two-body fragmentations of the s-hole of ^<11>B and ^<15>N are calculated to show the selection rule. The calculated escaping widths for the ^1B (s-hole) and ^<15>N (s-hole) doorway states are ingood correspondence with the experimental widths. This may suggest that the following scenario is realized ; in the light nuclei the fragmentation process of the s-hole state in the doorway stage is superior or competitive to that in the compound nuclear stage. Less