Particle and Astroparticle Physics Seminar

Ultracold neutrons and the nEDM: from Phonon excitaction to the Big Bang Theory and back to the Standard Model

Beatrice Franke

TRIUMF

The most remarkable feature of ultracold neutrons (UCN) are their very low energies of the order of nano-electronvolts. Being thus low-energetic, ultracold neutrons can also be confined in certain material bottles in order to be observed for several minutes. This facilitates the examination of some basic properties of the neutron. The flagship of UCN physics is the search for an electric dipole moment of the free neutron (nEDM). Beyond Standard Model theories predict nEDMs very close to the current upper limit of 3�10^-26 e�cm. Those predictions result from CP-violating processes, which in turn can be related to the matter-antimatter asymmetry observed in our universe. Thus the search for an nEDM contributes to understanding the Baryon asymmetry, as well as it has a high discovery potential for Beyond Standard Model physics.

The distinct feature of TRIUMFs UCN facility is the combination of a neutron spallation source with a superfluid helium UCN converter - unique among all existing and planned UCN sources worldwide. The goal of the UCN project at TRIUMF is to provide a density of several hundreds of UCN per cubic cm to experiments at up to two ports, whereas one will be dedicated to the search for the nEDM to the 10²⁷ e�cm level of precision. This presentation shall give an introduction to UCN physics, and update the audience on the current status of the new UCN facility at TRIUMF: the proton beamline and spallation target dedicated to UCN production have been commissioned successfully. Additionally, we were able to moderate neutrons to thermal and cold energies. First results of the commissioning process will be presented.