Scalar interaction limits from the beta-neutrino correlation of trapped   radioactive atoms
  We have set limits on contributions of scalar interactions to nuclear beta decay. 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 measurement of the beta-neutrino correlation, in a more direct fashion than previously possible. The beta-neutrino correlation parameter of the 0+ to 0+ pure Fermi decay of 38mK is $\tilde{a}$=0.9981+-0.0030+-0.0037, consistent with the standard model prediction a=1. 
A. Gorelov (1), D. Melconian (1), W.P. Alford (2), D. Ashery (3), G.   Ball (4), J.A. Behr (4), P.G. Bricault (4), J.M. D'Au...