Gamma-Ray Spectroscopy of ${}_{\Lambda }^{16}$O and ${}_{\Lambda }^{15}$N Hypernuclei via the ${}^{16}$O$(K^{-},{\pi }^{-})$ reaction

Abstract

he bound-state level structures of the ${}_{\Lambda }^{16}$O and ${}_{\Lambda }^{15}$N hypernuclei were studied by $\gamma$-ray spectroscopy using a germanium detector array (Hyperball) via the ${}^{16}$O ($K^{-},{\pi }^{-}\gamma$) reaction. A level scheme for ${}_{\Lambda }^{16}$O was determined from the observation of three $\gamma$-ray transitions from the doublet of states ($2^{-}$,$1^{-}$) at $\sim 6.7$ MeV to the ground-state doublet ($1^{-}$,$0^{-}$). The ${}_{\Lambda }^{15}$N hypernuclei were produced via proton emission from unbound states in ${}_{\Lambda }^{16}$O . Three $\gamma$ -rays were observed and the lifetime of the $1/2^{+};1$ state in ${}_{\Lambda }^{15}$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 ${}_{\Lambda }^{16}$O ground-state doublet spacing of 26.4 $\pm$ 1.6 $\pm$ 0.5 keV determines a small but nonzero strength of the $\Lambda N$ tensor interaction.

arXiv comment22 pages, 17 figures

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• Strangeness nuclear physics: a critical review on selected topics
• High Resolution Spectroscopy of 16N_Lambda by Electroproduction
• Shell-model calculations for p-shell hypernuclei
• Hyperons: the strange ingredients of the nuclear equation of state
• Hypernuclear spectroscopy with K${}^{-}$ at rest on ${}^7$Li, ${}^9$Be, ${}^{13}$C and ${}^{16}$O
• Search for ${}_{\Lambda }^6$H hypernucleus by the ${}^6$Li$({\pi }^{-},K^{+})$ reaction at $p_{{\pi }^{-}}$ = 1.2 GeV/$c$
• New results on Mesonic Weak Decay of $p$-shell $\Lambda$-Hypernuclei
• pi^- decay rates of p-shell hypernuclei revisited
• High-resolution hypernuclear spectroscopy at Jefferson Lab, Hall A
• First Determination of Level Structure of an $sd$-Shell Hypernucleus, ${}_{\mathrm{\Lambda }}^{19}\mathrm{F}$
• High Resolution Hypernuclear Spectroscopy at Jefferson Lab Hall A
• Structure of p-shell hypernuclei