Theoretical Investigation into Production of Double-Λ Hypernuclei from Stopped Ξ − on 6Li

Abstract

We have investigated theoretically a feasible nuclear reaction to produce light double-Λ hypernuclei by choosing a suitable target. In the reaction from stopped Ξ− on 6Li target light doubly-strange nuclei, \({^5_{\Lambda\Lambda}{\rm H}}\) and \({^6_{\Lambda\Lambda}{\rm He}}\), are produced: we have calculated the formation ratio of \({^5_{\Lambda\Lambda}{\rm H}}\) to \({^6_{\Lambda\Lambda}{\rm He}}\) for Ξ− absorptions from 2S, 2P and 3D orbitals of Ξ−–6Li atom by assuming a d−α cluster model for 6Li. From this cluster model the d−α relative wave functions has a node due to Pauli exclusion among nucleons belonging to d and α clusters. Two kinds of d−α wave functions, namely 1s relative wave function with a phenomenological one-range Gaussian (ORG) potential and that of an orthogonality-condition model (OCM) are used. It is found that the probability of \({^5_{\Lambda\Lambda}{\rm H}}\) formation is larger than that of \({^6_{\Lambda\Lambda}{\rm He}}\) for all absorption orbitals: in the case of the major 3D absorption their ratio is 1.08 for ORG and 1.96 for OCM. The dominant low momentum component of the d−α relative wave function favors the \({^5_{\Lambda\Lambda}{\rm H}}\) formation with a low Q value compared to the \({^6_{\Lambda\Lambda}{\rm He}}\) formation with a high Q value. We have also calculated momentum distributions of emitted particles, d and n, displaying continuum spectra for single-Λ hypernuclei, \({^4_{\Lambda}{\rm H}}\) and \({^5_{\Lambda}{\rm He}}\), and line spectra for the \({^5_{\Lambda\Lambda}{\rm H}}\) and \({^6_{\Lambda\Lambda}{\rm He}}\) nuclei. Thus, our present theoretical analysis would be a significant contribution to experiments in the strangeness −2 sector of hypernuclear physics.