UCNB : A measurement of the antineutrino- asymmetry using ultracold neutrons

Orateur : L. BROUSSARD (Los Alamos National Laboratory)

The Ultracold Neutron (UCN) facility at the Los Alamos Neutron Science Center uses one of the highest density sources of UCN in the world to perform precision measurements of neutron beta decay parameters. The UCNB experiment was designed to perform the first measurement of the antineutrino-asymmetry ``B" using ultracold neutrons, which is used to place limits on Beyond the Standard Model scalar and tensor interactions. The UCNB collaboration has worked jointly with the Nab collaboration to develop novel thick, large-area, highly segmented silicon detectors to detect the decay protons and electrons in coincidence. The detectors are installed in the 0.6T magnetic field region of the UCNA spectrometer, and the entire detection system is biased up to -30kV. The first proof of principle run of the experiment has recently been completed using one biased detector with 24 of the 128 detector pixels instrumented to detect protons and electrons, and a second unbiased detector with 8 pixels instrumented to detect coincident electrons and study backscattering effects. I will discuss preliminary results from the 2013-2014 data set including a first attempt to measure the antineutrino asymmetry, review the strategy for characterizing systematic effects, and outline the path forward.

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