The n3He experiment: Hadronic parity violation in cold neutron capture on 3He

The n3He experiment aims to measure the parity violating asymmetry in the direction of proton emission in the reaction n→+ ³He → ³H →+ p, using the capture of polarized cold neutrons in an unpolarized gaseous 3He target. Using effective field theory based calculations, the size of the asymmetry is estimated to be in the range of (-10→2)×10^-8, depending on the framework in which the calculations are done, and our goal measurement accuracy is 2×10^-8. The asymmetry is a result of the low energy weak interaction between nucleons and its measurement will provide a benchmark for modern effective field theory calculations in the isospin = 0 channel. The exper- iment uses a ³He multiwire ionization chamber as the combined target and detector, operated in current mode. The n3He experiment was installed and commissioned in December 2014 on the Fundamental Neutron Physics Beamline at the Spallation Neutron Source at Oak Ridge National Laboratory. The experiment is currently taking production data. In this paper, we provide an overview of the experiment and will show a few preliminary results of the data collected to date.