The decay path of the Hoyle state in 12C (Ex=7.654MeV) has been studied with the 14N(d,α2)12C(7.654) reaction induced at 10.5MeV. High resolution invariant mass spectroscopy techniques have allowed to unambiguously disentangle direct and sequential decays of the state passing through the ground state of 8Be. Thanks to the almost total absence of background and the attained resolution, a fully sequential decay contribution to the width of the state has been observed. The direct decay width is negligible, with an upper limit of 0.043% (95% C.L.). The precision of this result is about a factor 5 higher than previous studies. This has significant implications on nuclear structure, as it provides constraints to 3-α cluster model calculations, where higher precision limits are needed.
@article{arxiv.1705.09196,
title = {High precision probe of the fully sequential decay width of the Hoyle state in $^{12}$C},
author = {D. Dell'Aquila and I. Lombardo and G. Verde and M. Vigilante and L. Acosta and C. Agodi and F. Cappuzzello and D. Carbone and M. Cavallaro and S. Cherubini and A. Cvetinovic and G. D'Agata and L. Francalanza and G. L. Guardo and M. Gulino and I. Indelicato and M. La Cognata and L. Lamia and A. Ordine and R. G. Pizzone and S. M. R. Puglia and G. G. Rapisarda and S. Romano and G. Santagati and R. Spartà and G. Spadaccini and C. Spitaleri and A. Tumino},
journal= {arXiv preprint arXiv:1705.09196},
year = {2017}
}