Fundamental Symmetries

A New Measurement of the Electric Dipole Moment of the Neutron

P. R. Huffman, R. Golub, E. Korobkina, T. Rao, I. Berkutov, and collaborators in the nEDM Collaboration.
Our group plays a major role in an experimental program to develop a new technique to search for the neutron electric dipole moment (EDM). This technique offers an improvement in sensitivity of up to two orders of magnitude over existing measurements. A more precise value for this moment has the potential to challenge calculations that propose extensions to the Standard Model.


Fundamental Nuclear Physics Beamline at the SNS

P.R. Huffman, C.R. Gould, TUNL, R. Allen, V. Cianciolo, G.L. Greene, Oak Ridge National Laboratory, Oak Ridge, TN

The construction of the polychromatic cold beamline at the Fundamental Neutron Physics Beam Line (FNPB) facility at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is complete, and the neutron spectrum has been characterized.

The UCNA Experiment

H. O. Back, L. Broussard, C. R. Cottrell, J. Hoagland, A. T. Holley, R. W. Pattie,Jr., A. R. Young, TUNL
The UCNA collaboration obtained an extensive data set during the 2008 run period at LANSCE, providing the basis for a determination of the β-asymmetry in neutron decay at the 1% level. Systematic correctionsLANSCE and uncertainties were a central focus for this run, so in addition to polarization and background measurements, three different geometries for the detector and decay trap foils were implemented in order to characterize scattering and energy loss systematic corrections. The UCNA collaboration also published a preliminary, 5% measurement of the β-asymmetry (at the 67% confidence level), the first measurement of β-decay angular correlations using ultracold neutrons (UCNs). Running is underway to improve available UCN densities in the decay trap and to further reduce the uncertainty in the β-asymmetry.