The decay path of the Hoyle state in () has been studied with the reaction induced at 10.5 MeV. High resolution invariant mass spectroscopy techniques have allowed us to unambiguously disentangle direct and sequential decays of the state passing through the ground state of . 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 cluster model calculations, where higher precision limits are needed.
The three-body reaction has been studied in a kinematically complete experiment at from which indirect information on the two-body reaction at has been extracted by applying the Trojan horse method. The method used a recent improved formulation. The derived astrophysical factor for the two-body process is compared with that obtained from direct experiments.
The reaction was studied from down to astrophysical energies by means of the Trojan-horse method applied to the three-body reaction performed at an incident energy of . Coincidence spectra measured in a kinematically complete experiment show the presence of the quasifree process. The astrophysical factor for the reaction was extracted from the three-body cross section at low neutron momentum. The result was compared with the behavior of the astrophysical factor from the directly measured two-body reaction.
9 September 2011 in The Astrophysical Journal Letters