First determination of the isospin mixing in the 8Be 2+ doublet via 8B beta decay
Journal article, 2026
We report on the first experimental determination of the Fermi β strength in the β -decay of 8B, enabled by significant improvements in production yields at ISOLDE/CERN. This allows the direct observation of isospin mixing in the 16.6 and 16.9 MeV 2+ doublet in 8Be. Specifically, the 16.9 MeV state is resolved in β -decay for the first time with sufficient statistics to test a widely used two-level model. With the high statistics we could perform two independent analyses: one based on the observed β -strength distribution within the R-matrix framework, and a second based on the extracted β -recoil broadening. The latter makes it possible to extract the Fermi and Gamow-Teller strengths up to the electron-capture region. The obtained strengths are fully consistent with the two-state isospin mixing model.
Isospin structure
Beta decay study
Beta-delayed-alpha emission
Beta strength
Fermi and Gamow Teller transitions
Author
D. Fernández Ruiz
Spanish National Research Council (CSIC)
M. Borge
Spanish National Research Council (CSIC)
E. Nacher
Universitat de Valencia
Spanish National Research Council (CSIC)
O. Tengblad
Spanish National Research Council (CSIC)
S. Viñals
Spanish National Research Council (CSIC)
J. Benito
Complutense University
J. A. Briz
Complutense University
Spanish National Research Council (CSIC)
P. Figuera
National Institute for Nuclear Physics
L. M. Fraile
CERN
Complutense University
H. O. U. Fynbo
Aarhus University
A. Gad
Student at Chalmers
J. H. Jensen
Aarhus University
Erik Asbjörn Mikkelsen Jensen
Chalmers, Physics, Subatomic, High Energy and Plasma Physics
Aarhus University
Björn Jonson
Chalmers, Physics, Subatomic, High Energy and Plasma Physics
R. Lica
Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering
I. Marroquin
Spanish National Research Council (CSIC)
M. Munch
Aarhus University
J. S. Nielsen
Aarhus University
J. D. Ovejas
Spanish National Research Council (CSIC)
A. Perea
Spanish National Research Council (CSIC)
K. Riisager
Aarhus University
S. Sekal
CERN
University of Sciences and Technology Houari Boumediene (USTHB)
C. Sotty
Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
0370-2693 (ISSN)
Vol. 880 140791Subject Categories (SSIF 2025)
Subatomic Physics
DOI
10.1016/j.physletb.2026.140791