Study of some two-body non-mesonic decays of ${}_{\hat{I}}^4›$He and ${}_{\hat{I}}^5›$He

Abstract

The Non-Mesonic (NM) decay of ${}_{\hat{I}}^4›\mathrm{He}$ and ${}_{\hat{I}}^5›\mathrm{He}$ in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations are scarce. The ${}_{\hat{I}}^4›\mathrm{He}\to d+d,p+t$ decay channels simultaneously observed by FINUDA on several nuclei are compared: the $pt$ channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are $(1.37\pm 0.37)\times 10^{-5}/K_{stop}^{-}$ and $(8.3\pm 1.0)\times 10^{-5}/K_{stop}^{-}$, respectively. Due to the capability of FINUDA of identifying ${}_{\hat{I}}^5›\mathrm{He}$ hypernuclei, a few ${}_{\hat{I}}^5›\mathrm{He}\to d+t$ decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: $(3.0\pm 2.3)\times 10^{-3}$.

revised version, typos corrected, more figures inserted, more extended discussions in sections 3, 4. Errors in tab. 8 modified, yields + upper limits quoted. 16 pages, 8 figures, 2 tables