Improved limit on direct α decay of the Hoyle state

O.S. Kirsebom, H.O.U. Fynbo, K. Riisager, M. Alcorta, M.J.G. Borge, M. Cubero, D. Galaviz, M. Madurga, O. Tengblad, M. Turrión, C.A. Diget, B.R. Fulton, L.M. Fraile, B. Jonson, T. Nilsson, G. Nyman

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The current evaluation of the triple-α reaction rate assumes that the α decay of the 7.65 MeV, 0 state in C12, commonly known as the Hoyle state, proceeds sequentially via the ground state of Be8. This assumption is challenged by the recent identification of two direct α-decay branches with a combined branching ratio of 17(5)%. If correct, this would imply a corresponding reduction in the triple-α reaction rate with important astrophysical consequences. We have used the B11(He3,d) reaction to populate the Hoyle state and measured the decay to three α particles in complete kinematics. We find no evidence for direct α-decay branches, and hence our data do not support a revision of the triple-α reaction rate. We obtain an upper limit of 5×10 3 on the direct α decay of the Hoyle state at 95% C.L., which is 1 order of magnitude better than a previous upper limit. © 2012 American Physical Society.
Original languageEnglish
Article number202501
Pages (from-to)1-4
Number of pages4
JournalPhysical Review Letters
Issue number20
Publication statusPublished - 14 May 2012

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