Rare 40K decay with implications for fundamental physics and geochronology

M. Stukel; L. Hariasz; P.C.F. Di Stefano; B.C. Rasco; K.P. Rykaczewski; N.T. Brewer; D.W. Stracener; Y. Liu; Z. Gai; C. Rouleau; J. B. Carter; J. Kostensalo; J. Suhonen; H. Davis; E.D. Lukosi; K.C. Goetz; R.K. Grzywacz; M. Mancuso; F. Petricca; A. Fijalkowska; M. Wolinska-Cichocka; J. Ninkovic; P. Lechner; R.B. Ickert; Leah E. Morgan; P.R. Renne; I. Yavin

doi:10.1103/PhysRevLett.131.052503

Rare 40K decay with implications for fundamental physics and geochronology

Physical Review Letters

By: M. Stukel, L. Hariasz, P.C.F. Di Stefano, B.C. Rasco, K.P. Rykaczewski, N.T. Brewer, D.W. Stracener, Y. Liu, Z. Gai, C. Rouleau, J. B. Carter, J. Kostensalo, J. Suhonen, H. Davis, E.D. Lukosi, K.C. Goetz, R.K. Grzywacz, M. Mancuso, F. Petricca, A. Fijalkowska, M. Wolinska-Cichocka, J. Ninkovic, P. Lechner, R.B. Ickert, Leah E. Morgan, P.R. Renne, and I. Yavin

https://doi.org/10.1103/PhysRevLett.131.052503

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Abstract

Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts subatomic rare-event searches, nuclear structure theory, and estimated geological ages. A predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The KDK (potassium decay) collaboration reports strong evidence of this rare decay mode. A blinded analysis reveals a nonzero ratio of intensities of ground-state electron-captures ( $I_{{EC}^{0}}^{0}$ ) over excited-state ones ( $I_{{EC}^{*}}^{*}$ ) of $I_{{EC}^{0}}^{0} / I_{{EC}^{*}}^{*} = 0.0095 stat \pm 0.0022 sys \pm 0.0010$ (68% C.L.), with the null hypothesis rejected at $4 σ$ . In terms of branching ratio, this signal yields $I_{{EC}^{0}}^{0} = 0.098 % stat \pm 0.023 % sys \pm 0.010 %$ , roughly half of the commonly used prediction, with consequences for various fields [L. Hariasz et al., companion paper, Phys. Rev. C 108, 014327 (2023)].

Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Rare 40K decay with implications for fundamental physics and geochronology
Series title	Physical Review Letters
DOI	10.1103/PhysRevLett.131.052503
Volume	131
Publication Date	July 31, 2023
Year Published	2023
Language	English
Publisher	American Physical Society
Contributing office(s)	Geology, Geophysics, and Geochemistry Science Center
Description	052503