A new high-precision upper limit of direct α-decays from the Hoyle state in 12C
1 Dip. di Fisica “E. Pancini”, Università di Napoli Federico II, I-80126 Napoli, Italy
2 INFN-Sezione di Napoli, I-80126 Napoli, Italy
3 Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex, France
4 INFN - Sezione di Catania, Via S. Sofia, I-95125 Catania, Italy
5 Universidad Nacional Autónoma de México, A.P. 20-364, Cd.Mx, D.F. 01000 México
6 INFN - Laboratori Nazionali del Sud, Via S. Sofia, I-95125 Catania, Italy
7 Dip. di Fisica e Astronomia, Università di Catania, Via S. Sofia, I-95125 Catania, Italy
8 Facoltà di Ingegneria ed Architettura, Università Kore, I-94100 Enna, Italy
* e-mail: email@example.com
Published online: 30 December 2017
The Hoyle state in 12C(Ex = 7.654MeV) is characterized by a pronounced 3α cluster configuration. It is involved in the so-called 3α process in stars, that is responsible of 12C nucleosynthesis. We studied the decay path of the Hoyle state by using the 14N(d, α2)12C(7.654) reaction at 10.5MeV incident energy. We found, with a precision higher of a factor 5 than any other previous experiment, an almost total absence of direct decays by-passing the ground state of 8Be. A new upper limit of such a decay width is placed at 0.043% (95% C.L.). Astrophysical 3α process reaction rate calculations have to be consequently revised.
© The Authors, published by EDP Sciences, 2017
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