Fundamental physics with cold neutron beams

The neutron exhibits rich physics both as a tool for studying materials, particle and nuclear physics, as well as the object of experimental study. The neutron lifetime is an important input to Big Bang Nucleosynthesis models and is currently known only to approximately 0.3\% with the most precise measurements from two different experimental techniques in disagreement by more than 3$\sigma$ [sigma]. Parity violation has been the subject of study since its discovery in 1957. Parity violation experiments provide access to studying the hadronic weak interaction, which is otherwise suppressed by several orders of magnitude below that of the strong interaction. It is the hadronic weak interaction that the NPDGamma experiment accesses via studying the asymmetry in gamma ray emission from the capture of polarized neutrons on liquid parahydrogen. Finally, as part of the NPDGamma experiment, the opportunity arose to use the well known and characterized apparatus for conducting a measurement of the liquid parahydrogen scattering cross section which has important implications in the design of neutron sources and moderators at cold neutron research facilities.