Observation of Hypernuclear Gamma-Ray Transitions in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Li</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow><mml:mi>Λ</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow><mml:mi>Λ</mml:mi></mml:mrow><mml:mrow><mml:mn>9</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>

Abstract

$\ensuremath{\gamma}$-ray transitions of energy 2.034 \ifmmode\pm\else\textpm\fi{} 0.023 MeV in the hypernucleus $_{\ensuremath{\Lambda}}^{7}\mathrm{Li}$ and 3.079 \ifmmode\pm\else\textpm\fi{} 0.040 MeV in the hypernucleus $_{\ensuremath{\Lambda}}^{9}\mathrm{Be}$ are observed. In both cases, the energy of the $\ensuremath{\gamma}$ ray in the hypernucleus $_{\ensuremath{\Lambda}}^{A}Z$ is very close to the energy of the first excited state of the nuclear core. The $\ensuremath{\gamma}$ rays are interpreted as arising from core transitions in the presence of the $\ensuremath{\Lambda}$ particle. The size of the shift places limits on the strength of the $\ensuremath{\Lambda}N$ spin-dependent interaction.