Precise determination of 12 A C level structure by γ-ray spectroscopy

Abstract

The 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 12C(π + , K+ γ ) reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet (2- , 1- 1 ) was measured to be 161.5 ± 0.3(stat) ± 0.3(syst) keV from the direct M1 transition. Excitation energies of the 1- 2 and 1- 3 states were measured to be 2832 ± 3 ± 4 keV and 6050 ± 8 ± 7 keV, respectively. The level energies obtained provide definitive references for the reaction spectroscopy of λ hypernuclei.