T Violation in the weak scalar and tensor interaction: neutron and nuclei

The motivation and status of a search for time-reversal violation in nuclear and neutron beta decay are discussed. A new experiment for free neutron decay is proposed. A hitherto unmeasured amplitude, R, of the directional correlation J·( p×σ), between the neutron spin J, the electron momentum p and the electron spin σ, will be determined. An accuracy well below 0.01 can be achieved using an intense cold neutron beam and an electron tracking detector, where the spin sensitivity is provided by large angle Mott scattering. This study provides an unique access to the exotic scalar S and tensor T interaction. Finite values, or tight constraints on the time-reversal violating scalar components, can be deduced in a combined analysis of the proposed experiment and a precise determination of the tensor couplings from a recent study of 8Li decay. The great interest in weak scalar interaction is stimulated by a multitude of scalar bosons which are introduced in most extensions of the Standard Model.