A Measurement of the Parity Violating Proton Asymmetry in the Capture of Polarized Cold Neutrons on 3He.

We propose a measurement the parity violating asymmetry Ap of the correlation between the longitudinal polarization of incoming cold neutrons (~σn) and the outgoing momentum of protons (~kp) after nuclear breakup in the reaction ~n + 3 He → p + T + 765 keV. The asymmetry is directly related to the weak nucleon-nucleon coupling which is of fundamental interest in the verification of the meson exchange model of NN interactions, as well as in the verification of several emerging χPT based effective field theory models. The reaction is well suited to these purposes because the PV asymmetry is expected to be large and the nuclear structure can be accurately treated using few-body methods. Testing these models can provide new and important information about QCD at low energy and how it modifies the weak interaction. We estimate the size of the asymmetry to be around 3×10−7, based on estimates, scaling from p-p scattering, in the scattering states, and a calculation of the bound state asymmetry. We argue that it is possible to measure the asymmetry to an accuracy of about 2 × 10−8 in ≈ 107 sec. We provide a reference design of the experiment and sho