Improved Limit on Direct α Decay of the Hoyle State
Journal article, 2012

The current evaluation of the triple-α reaction rate assumes that the α decay of the 7.65 MeV, 0+ state in 12C, commonly known as the Hoyle state, proceeds sequentially via the ground state of 8Be. 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 11B(3He,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.


O. S. Kirsebom

M. Alcorta

M. J. G. Borge

M. Cubero

C. Aa Diget

L. M. Fraile

B. R. Fulton

H. O. U. Fynbo

D. Galaviz

Björn Jonson

Chalmers, Applied Physics, Subatomic Physics

M. Madurga

Thomas Nilsson

Chalmers, Applied Physics, Subatomic Physics

Göran Hugo Nyman

Chalmers, Applied Physics, Subatomic Physics

K. Riisager

Olof Tengblad

M. Turrión

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 108 20 202501- 202501

Subject Categories

Subatomic Physics

Physical Sciences

Astronomy, Astrophysics and Cosmology


Basic sciences



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