M. Trinczek

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

Laser trapping and cooling techniques are now being applied to the study of nuclear β-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 β. This allows reconstruction of the neutrino momentum, and the deduction of the β-v 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-β+ coincidences from the 0+ → 0+ pure Fermi decay of 38mK, 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 β-v correlation experiments.

Beta-decay experiments of neutral atoms in a magneto-optical trap

Magneto optical traps (MOT) allow the cooling and storing of neutral atoms in a volume of a few cubic millimeters by use of laser beams and a magnetic field. Such devices offer new and exciting opportunities for precision measurements of radioactive isotopes. Here we present experiments performed with a double-MOT system coupled to the on-line separator TISOL at TRIUMF/Vancouver, Canada. For the first time, the Β-decay of free atoms stored in such a device could be observed. We report on coincidence measurements between beta-particles and the argon recoils in the decay of 37K and 38rm{m}}K. The charge state ratios of the recoil-ions were deduced by Time-Of-Flight separation in an acceleration field. The final goal of those investigations is a precision test of the Standard Model by measuring the –nu-correlation parameter a.

Search for scalar contributions to the 38mKβ+−ν correlation in a magneto-optic trap

We have begun a program to test weak interaction symmetries by trapping in a Magneto-optic trap (MOT) isotopes produced at the TRIUMF cyclotron’s on-line separator TISOL. We are searching for non-Standard Model scalar contributions to the β+−ν correlation in the 0+→0+ Fermi decay of 38mK. We have trapped 38mK and 37K in a vapor-cell MOT, and transferred them to a second MOT which houses the nuclear detectors. The recoiling nuclei freely escape the trap and are detected in a microchannel plate; simultaneous detection of the β+ momentum allows reconstruction of the ν momentum. Approximately 500,000 β+-recoil coincidences have been observed in June 1998; analysis is proceeding.