Searching for the electron EDM in a storage ring

Searches for permanent electric dipole moments (EDM) of fundamental particles have been underway for more than 50 years with null results. Still, such searches are of great interest because EDMs arise from radiative corrections involving processes that violate parity and time-reversal symmetries, and through the CPT theorem, are sensitive to CP-violation. New models of physics beyond the standard model predict new sources of CP-violation leading to dramatically enhanced EDMs possibly within the reach of a new generation of experiments. We describe a new approach to electron EDM searches using molecular ions stored in a tabletop electrostatic storage ring. Molecular ions with long-lived paramagnetic states such as tungsten nitride WN⁺ can be injected and stored in larger numbers and with longer coherence times than competing experiments, leading to high sensitivity to an electron EDM. Systematic effects mimicking an EDM such as those due to motional magnetic fields and geometric phases are found not to limit the approach in the short term, and sensitivities of δ|d_e| ≈ 10⁻³⁰ e·cm/day appear possible under conservative conditions.