Measurement of Gamma-Rays from 11 Λ B and 12 Λ C

From the 12C(π+, K+)12ΛC reaction, the γ-rays of 261.6±0.24 keV (7/2+→5/2+) and 1481.7±0.7 keV (1/2+→5/2+) of 11ΛB, and 2667.3±2.8 keV (12−→21−) of 12ΛC hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7 keV and 261.6 keV are significantly different from the values predicted by the shell model using the Δ and SN parameters determined from the 7ΛLi data.