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arXiv · 1706.00414

Precision measurement of the $\beta$-asymmetry in spin-polarized $^{37}\mathrm{K}$ decay

B. Fenker·A. Gorelov·D. Melconian·J. A. Behr·M. Anholm·D. Ashery·R. S. Behling·I. Cohen·I. Craiciu·G. Gwinner·J. McNeil·M. Mehlman·K. Olchanski·P. D. Shidling·S. Smale·C. L. Warner
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Abstract

Using TRIUMF's neutral atom trap, TRINAT, for nuclear $\beta$ decay, we have measured the $\beta$ asymmetry with respect to the initial nuclear spin in $^{37}\mathrm{K}$ to be $A_\beta=-0.5707(13)_\mathrm{syst}(13)_\mathrm{stat}(5)_\mathrm{pol}$, a 0.3% measurement. This is the best relative accuracy of any $\beta$-asymmetry measurement in a nucleus or the neutron, and is in agreement with the standard model prediction $-0.5706(7)$. We compare constraints on physics beyond the standard model with other $\beta$-decay measurements, and improve the value of $V_\mathrm{ud}$ measured in this mirror nucleus by a factor of 4.

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B. Fenker, A. Gorelov, D. Melconian, J. A. Behr, M. Anholm, D. Ashery, R. S. Behling, I. Cohen, I. Craiciu, G. Gwinner, J. McNeil, M. Mehlman, K. Olchanski, P. D. Shidling, S. Smale, C. L. Warner. 2017-06-01. Precision measurement of the $\beta$-asymmetry in spin-polarized $^{37}\mathrm{K}$ decay. https://doi.org/10.1103/physrevlett.120.062502

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