W. Imoto | Searcharxiv

arXiv2015

Precise determination of $^{12}_Λ$C level structure by $γ$-ray spectroscopy

Level structure of the $^{12}_Λ$C hypernucleus was precisely determined by means of $γ$-ray spectroscopy. We identified four $γ$-ray transitions via the $^{12}$C$(π^{+},K^{+}γ)$ reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet $(2^{-}_{1},1^{-}_{1})$ was measured to be $161.5\pm0.3\text{(stat)}\pm0.3\text{(syst)}$\,keV from the direct $M1$ transition. Excitation energies of the $1^{-}_{2}$ and $1^{-}_{3}$ states were measured to be $2832\pm3\pm4$\,keV and $6050\pm8\pm7$\,keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of $Λ$ hypernuclei.

nucl-ex↗

arXiv2012

Search for a bound state of kaon and pion

We have searched for a bound state of kaon and pion denoted by $X$. The $X$ was conjectured to explain the so-called $Θ^+$ resonance as a bound state of kaon, pion and nucleon. This model explains almost all properties of the $Θ^+$, however, the model works only if the $K π$ interaction is strongly attractive. It is so strong that it could make a bound state $X$. Here we report a result of the search for the $X$ by using the $K^+ + N \rightarrow X^+ + N$ reaction at P$_K\sim$ 1.2 GeV/c. The $X^+ \rightarrow K^+ γγ$ decay produces $K^+$ in momentum region where other processes cannot fill. We observed signature of the $X^+$ with statistical significance of 2 $σ$. Production cross section of $X$ with respect to that of $π^0$ is 1$\pm$0.5% if we take it as an evidence and 1.5% if we set an upper limit.

hep-ex↗