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Published on: June 28, 2018
Precision Measurement of the β Asymmetry in Spin-Polarized ^{37}K Decay
B Fenker1,2, A Gorelov3, D Melconian1,2
1Cyclotron Institute, Texas A&M University, 3366 TAMU, College Station, Texas 77843-3366, USA.
Abstract:
Using Triumf's neutral atom trap, Trinat, for nuclear β decay, we have measured the β asymmetry with respect to the initial nuclear spin in ^{37}K to be A_{β}=-0.5707(13)_{syst}(13)_{stat}(5)_{pol}, a 0.3% measurement. This is the best relative accuracy of any β-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 β-decay measurements, and improve the value of V_{ud} measured in this mirror nucleus by a factor of 4.
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