Beta-neutrino correlation experiments on laser trapped 38mK, 37K

Laser trapping and cooling techniques are now being applied to the study of nuclear beta-decay at several labs. A magneto-optical trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the deduction of the beta-nu correlation in a more direct fashion than previously possible. In addition, the nuclei can be polarized by atomic techniques, opening a new class of spin-correlation measurements to test the degree to which parity is maximally violated in the weak interaction. Our present experiment has detected several hundred thousand recoil-beta(+) coincidences from the 0(+) --> 0(+) pure Fermi decay of K-38m, produced at the on-line isotope separators TISOL and ISAC at TRIUMF. Our goal is to set constraints on non-Standard Model scalar bosons competitive with high-energy colliders and more conventional beta-nu correlation experiments.