Revalidation of the isobaric multiplet mass equation for the $A=20$ quintet

B. E. Glassman; D. Pérez-Loureiro; C. Wrede; J. Allen; D. W. Bardayan; M. B. Bennett; B. A. Brown; K. A. Chipps; M. Febbraro; C. Fry; M. R. Hall; O. Hall; S. N. Liddick; P. O'Malley; W. Ong; S. D. Pain; S. B. Schwartz; P. Shidling; H. Sims; P. Thompson; H. Zhang

doi:10.1103/physrevc.92.042501

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arXiv · 1511.01809

Revalidation of the isobaric multiplet mass equation for the $A=20$ quintet

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Abstract

An unexpected breakdown of the isobaric multiplet mass equation in the $A=20$, $T=2$ quintet was recently reported, presenting a challenge to modern theories of nuclear structure. In the present work, the excitation energy of the lowest $T = 2$ state in $^{20}$Na has been measured to be $6498.4 \pm 0.2_{\textrm{stat}} \pm 0.4_{\textrm{syst}}$ keV by using the superallowed $0^+ \rightarrow 0^+$ beta decay of $^{20}$Mg to access it and an array of high-purity germanium detectors to detect its $γ$-ray deexcitation. This value differs by 27 keV (1.9 standard deviations) from the recommended value of $6525 \pm 14$ keV and is a factor of 28 more precise. The isobaric multiplet mass equation is shown to be revalidated when the new value is adopted.

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B. E. Glassman, D. Pérez-Loureiro, C. Wrede, J. Allen, D. W. Bardayan, M. B. Bennett, B. A. Brown, K. A. Chipps, M. Febbraro, C. Fry, M. R. Hall, O. Hall, S. N. Liddick, P. O'Malley, W. Ong, S. D. Pain, S. B. Schwartz, P. Shidling, H. Sims, P. Thompson, H. Zhang. 2015-11-05. Revalidation of the isobaric multiplet mass equation for the $A=20$ quintet. https://doi.org/10.1103/physrevc.92.042501

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