Neutron Electric Dipole Moment Search by the TUCAN collaboration

Permanent electric diopole moments (EDM) in fundamental particles violate time reversal symmetry. Under CPT conservation, T violation implies CP violation. A precise measurement of an EDM may reveal the origin of matter dominate universe.

The TUCAN (TRIUMF Ultra-Cold Advanced Neutron source) collaboration aims to measure a neutron EDM at a sensitivity of $10^{-27}$ ecm, which is a 30 times better sensitivity than the current best measurement. The neutron EDM has been searched for using Ultracold Neutrons (UCN). UCNs are extremely slow neutrons which have a kinetic energy below several hundred neV. As a consequence, UCNs are totally reflected at the surface of certain materials and can be confined in a material bottle.

Since a neutron EDM measurement sensitivity is limited by statistics, the TUCAN collaboration has been developing a high intensity UCN source on a dedicated proton beam line at TRIUMF. The UCN source is composed of a combination of a spallation neutron source and a superfluid helium UCN converter. First UCN production succeeded at TRIUMF in November 2017. Following this success, we have started to upgrade the UCN source and aim for a world’s highest intensity. Key components of the improvement are a new helium cryostat to remove high radiation heat load from the superfluid helium UCN converter and thus allow for higher proton beam currents on the spallation target. Furthermore, a liquid deuterium moderator shall be added in order to get a higher cold neutron flux at the location of the converter.

In this presentation, the current status of the UCN source upgrading and experiment plans of the neutron EDM measurement will be discussed.