Precision β decay experiments represent an important and complimentary approach to high‐energy searches for physics outside the “Standard Model”, our current understanding of fundamental particles and their interactions. The mirror decay of 37K provides an excellent probe with which to search for new physics. The ft value of this (as well as other T = 1/2 mirror transitions) can be used to provide a measurement of the value of the Vud element of the CKM mass‐mixing matrix, complementing the value obtained from superallowed pure Fermi decays. In addition, the polarized angular distribution parameters are sensitive to a variety of possible new physics: the β and ν asymmetries can be used to search for right‐handed currents in the charged weak interaction, and their energy‐dependences are sensitive to second‐class currents forbidden in the Standard Model. Time‐reversal symmetry can also be tested by a precision measurement of the triple‐vector correlation between the initial nuclear spin and the momenta of t...
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