Proposed measurement of the beta-neutrino correlation in neutron decay

Abstract

Currently, the beta-neutrino asymmetry has the largest uncertainty (4 %) of the neutron decay angular correlations. Without requiring polarimetry, this decay parameter can be used to measure λ (ga/gvv), test Cabibbo-Kobayashi-Maskawa (CKM) unitarity, limit scalar and tensor currents, and search for Charged Vector Current (CVC) violation. We propose to measure the beta-neutrino asymmetry coeffcient, a, using time-of-flight for the recoil protons. We hope to achieve a systematic uncertainty of σa / a ≈ 1.0%. After tests at Indiana University's Low Energy Neutron Source (LENS), the apparatus will be moved to the National Institute of Standards and Technology (NIST) where the measurement can achieve a statistical uncertainty of 1 % to 2 % in about 200 beam days.