{gamma}-ray spectroscopy of {sub {lambda}}{sup 16}O and {sub {lambda}}{sup 15}N hypernuclei via the {sup 16}O(K{sup -},{pi}{sup -}{gamma}) reaction

The bound-state level structures of the {sub {lambda}}{sup 16}O and {sub {lambda}}{sup 15}N hypernuclei were studied by {gamma}-ray spectroscopy using a germanium detector array (Hyperball) via the {sup 16}O (K{sup -},{pi}{sup -}{gamma}) reaction. A level scheme for {sub {lambda}}{sup 16}O was determined from the observation of three {gamma}-ray transitions from the doublet of states (2{sup -},1{sup -}) at {approx}6.7 MeV to the ground-state doublet (1{sup -},0{sup -}). The {sub {lambda}}{sup 15}N hypernuclei were produced via proton emission from unbound states in {sub {lambda}}{sup 16}O. Three {gamma} rays were observed, and the lifetime of the 1/2{sup +};1 state in {sub {lambda}}{sup 15}N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin dependence of the {lambda}N interaction is discussed. In particular, the measured {sub {lambda}}{sup 16}O ground-state doublet spacing of 26.4{+-}1.6{+-}0.5 keV determines a small but nonzero strength of the {lambda}N tensor interaction.