Measurement of the β-ν correlation using magneto-optically trapped 21Na -: art. no. 102501

The beta-neutrino correlation coefficient, a(betanu), in Na-21 is inferred from detecting the beta(+) and low-energy recoil daughter nucleus. Na-21 is produced at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory and 800 000 atoms are maintained in a magneto-optical trap. From the measured time of flight of recoil ions in the presence of a drift electric field, we find a(betanu)=0.5243+/-0.0091. There may be a dependence on the trapped atom population. This and other systematic uncertainties are discussed.