21-23 March 2022
Europe/Madrid timezone

Consistency tests of the β+ decay of 8B with the R-Matrix formalism

21 Mar 2022, 17:45
Red Temática de Física Nuclear (FNUC) Red FNUC (Red Temática de Física Nuclear)


Daniel Fernandez Ruiz (IEM-CSIC)


The study of 8B is of interest for both astrophysics and nuclear structure. From the astrophysical point of view, 8B is part of the hydrogen-burning chain that occurs inside the stars [1]. In addition, its decay is the source of high-energy solar neutrinos above 2 MeV being it the main contributor to what was known as the “solar neutrino problem” [2]. On the nuclear structure side, the β+ decay of 8B opens a window to the structure of 8Be. 8Be contains two notable features in the QEC-window of 8B: a broad 2+ state at 3 MeV [3] and a 2+ isospin doublet formed by its 16.6 and 16.9 MeV relatively narrow levels, the only known case of almost equal isospin mixing between nuclear states [4]. These three 2+ levels break in two α particles, gives rise to an α-continum spectrum.

Our team, in collaboration with our colleges of the MAGISOL (Madrid-Aarhus-Goteborg at ISOLDE) group, has conducted multiple experiments to study the structure of the 8Be nucleus, the most recent one is the IS633 experiment [5], which took place in May of 2017 at the ISOLDE facility at CERN in Switzerland. Its main goal was to characterize the feeding to the 2+ isospin doublet of 8Be through the β+ decay of 8B; the results were analysed by S.Viñals [5]. The feeding to the doublet was resolved for first time in a beta-decay work. The feeding to the 2+ states in 8Be was analysed using the R-Matrix formalism. This analysis concluded that, the 16.6 and 16.9 MeV states of 8Be are completely isospin mixed [6], in accordance with the theoretical predictions.

In this contribution, we present the current results and a continuation of the R-matrix analysis; in this new approach, we have imposed a series of constraints upon our data with the aim of testing the consistency of the present results when compared with previous experiments [7].

Primary author


Maria Jose Garcia Borge (ISOLDE-CERN) Prof. Olof Tengblad (IEM - CSIC) Sílvia Viñals Onsès (CSIC - IEM)

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