Polarized Ultra-Cold Neutron Transport for Neutron Beta Decay Asymmetry Measurements

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Nuclear beta decay was important in motivating the Standard Model, and it continues to be of importance in searches for physics beyond the Standard Model. The simplest system for studying beta decay is the neutron. By measuring the neutron's lifetime (from the Ft value) and the neutron's beta asymmetry A, one has enough information to independently determine the weak vector and axial-vector couplings, GV and GA. An approved experiment (located at Los Alamos) will again measure the A coefficient, utilizing Ultra-Cold Neutrons (UCN), dramatically reducing systematic errors otherwise present due to beam-induced backgrounds and incomplete polarization. The key features are 1) the ability to port the neutrons to a significant distance away from their production site, 2) vetoing events when the beam pulse is on target, and 3) obtain 100% polarization using an axial magnetic field. This proposal covers efforts to develop an optimum coating for transporting polarized neutrons, and implementing a suitable DAQ system for the experiment. It appears pulsed-laser-deposition (PLD) diamond films may be suitable. A successful campaign to make suitably coated guides would have an significant impact, not just for this experiment, but planned future experiments as well. 5