The β⁺ decay of ³⁷K as a multi-faceted probe of fundamental physics

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 V_ud 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 the leptons. An overview of the variety of physics that can be probed using laser-cooled ³⁷K and the techniques used to perform the precision measurements is presented.