Scalar interaction limits from the β-ν correlation of trapped radioactive atoms -: art. no. 142501

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap 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 measurement of the beta-nu correlation, in a more direct fashion than previously possible. The beta-nu correlation parameter of the 0(+)-> 0(+) pure Fermi decay of K-38(m) is (a) over tilde = 0.9981 +/- 0.0030(-0.0037)(+0.0032), consistent with the standard model prediction (a) over tilde =1.