Ultra-cold neutrons (UCN) have velocities of a few meters per second and can be confined in bottles of certain materials or in strong magnetic fields. The ability to trap neutrons allows high precision experiments testing their properties. I will discuss a new source of UCN at the LANSCE facility that is being constructed to measure the electron asymmetry from polarized neutron decay (the so-called A-correlation). This experiment will provide a new measurement of the quark electro-weak mixing (Vud) that is competitive with 0+ - 0+ nuclear decays but free of nuclear corrections. I will also discuss a second-generation source that could provide significantly higher UCN densities for a number of novel physics opportunities.

ANL Physics Division Colloquium Schedule