K. Agari | Searcharxiv

arXiv2020

Observation of Coulomb-assisted nuclear bound state of $\Xi^-$-$^{14}$N system

In an emulsion-counter hybrid experiment performed at J-PARC, a $\Xi^-$ absorption event was observed which decayed into twin single-$\Lambda$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $\Xi^{-} + ^{14}$N$\ \rightarrow\ ^{10}_\Lambda$Be + $^5_\Lambda$He. For the binding energy of the $\Xi^{-}$ hyperon in the $\Xi^-$-$^{14}$N system a value of $1.27 \pm 0.21$ MeV was deduced. The energy level of $\Xi^-$ is likely a nuclear $1p$ state which indicates a weak ${\Xi}N$-$\Lambda\Lambda$ coupling.

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arXiv2019

Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

A double-$Λ$ hypernucleus, ${}_{ΛΛ}\mathrm{Be}$, was observed by the J-PARC E07 collaboration in nuclear emulsions tagged by the $(K^{-},K^{+})$ reaction. This event was interpreted as a production and decay of $ {}_{ΛΛ}^{\;10}\mathrm{Be}$, ${}_{ΛΛ}^{\;11}\mathrm{Be}$, or ${}_{ΛΛ}^{\;12}\mathrm{Be}^{*}$ via $Ξ^{-}$ capture in ${}^{16}\mathrm{O}$. By assuming the capture in the atomic 3D state, the binding energy of two $Λ$ hyperons$\,$($B_{ΛΛ}$) of these double-$Λ$ hypernuclei are obtained to be $15.05 \pm 0.11\,\mathrm{MeV}$, $19.07 \pm 0.11\,\mathrm{MeV}$, and $13.68 \pm 0.11\,\mathrm{MeV}$, respectively. Based on the kinematic fitting, ${}_{ΛΛ}^{\;11}\mathrm{Be}$ is the most likely explanation for the observed event.

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