The nEDM experiment at the SNS

The nEDM collaboration proposes to measure the neutron electric dipole moment at the Spallation Neutron Source (Oak Ridge National Laboratory). The nEDM is a clear signature of CP violation. According to the Standard Model the nEDM is very small (∼10⁻³¹ e cm), but many theories predict much higher values. In the proposed experiment polarized cold neutrons from the SNS would be trapped in liquid helium at a temperature of about 400 mK. The neutron spin would precess in a very uniform magnetic field (H ∼ 30 mG), and the experiment would measure the change in the precession frequency when a very strong electric field (E ∼ 50 kV/cm) is applied. Polarized ³He atoms serve as a co-magnetometer. The goal of the experiment is to measure the nEDM with an accuracy of ∼9 × 10⁻²⁸ e cm, which is more than an order of magnitude better than existing results.