Precise determination of $^{12}_{\Lambda}$C level structure by $\gamma$-ray spectroscopy

TL;DR

This study precisely measured the energy levels of the $^{12}_{ ext{Lambda}}$C hypernucleus using gamma-ray spectroscopy, providing definitive reference data for hypernuclear reaction studies.

Contribution

The paper presents the first precise measurement of the $^{12}_{ ext{Lambda}}$C level structure using gamma-ray spectroscopy, including the ground-state doublet spacing and excited state energies.

Findings

Ground-state doublet spacing measured as 161.5 keV.

Excited states $1^{-}_2$ and $1^{-}_3$ energies determined.

Provides reference data for hypernuclear reaction spectroscopy.

Abstract

Level structure of the $^{12}_{\Lambda}$C hypernucleus was precisely determined by means of $\gamma$-ray spectroscopy. We identified four $\gamma$-ray transitions via the $^{12}$C$(\pi^{+},K^{+}\gamma)$ 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 $\Lambda$ hypernuclei.