Refuting the nature of the sixth 0+ Hoyle-analogue state candidate in 16O

A prominent candidate for a Hoyle-analogue state in 16O is the 0+ 6 state, previously observed at Ex = 15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-α cluster state, analogous to the Hoyle state in 12C. Whilst much theoretical work has been performed to reconcile a calculated α-cluster state with this resonance, the experimental information on this state remained very scarce. To investigate this state, the 16O(α, α') reaction was studied at θlab = 0° at an incident energy of Elab = 200 MeV using the K600 magnetic spectrometer at iThemba LABS. For the first time, the decay channels of the Ex = 15.097(5) MeV state were isolated using a large acceptance silicon-strip detector array at backward angles. The lineshapes of the states were analysed within a phenomenological R-matrix framework. Results indicate the presence of a resonance at Ex ≈ 15 MeV which does not exhibit a Jπ = 0+ nature.