Highly-polarized laser-cooled ⁴⁷K and ³⁷K for beta decay studies of isospin, parity, and time-reversal breaking

Improving upon our previous work [B. Fenker et al. New Journal of Physics 2016], we have achieved and measured by atomic methods nuclear spin vector polarization 0.96+-0.04 for ⁴⁷K and 0.997+-0.002 for ³⁷K. Our method compares atomic excited state excitation of circular and linearly polarized light using the 4S to 4P1/2 transition, and worked by long integration times on about 1,000 laser-trapped atoms. Preliminary results on the asymmetry of progeny nuclei from polarized ³⁷K decay, sensitive to beta and neutrino relative helicity, will be shown in J. McNeil's talk. Here we will concentrate in isospin breaking and future time-reversal in ⁴⁷ K. We will also show first results from a beta-neutrino-gamma time-reversal-breaking correlation in ³⁷K decay.