False EDM effects in PSI nEDM: Leakage Currents and Background Asymmetries

Abstract

The Paul Scherrer Institute Neutron Electric Dipole Moment (PSI nEDM) experiment is a room temperature experiment using the Ramsey technique of separated oscillating fields to search for a permanent electric dipole moment in neutrons. The PSI nEDM experiment achieved a statistical sensitivity of d_n < 1.1 * 10^{-26} e.cm using data collected from 2015 to 2016. The magnetic field produced by currents flowing near the precession chamber couple to the spin of the stored neutrons. Currents which are correlated with the electric field may induce a false measurable EDM. Candidates for currents which are correlated with high voltage are leakage currents originating from the high voltage system used to apply a strong electric field to the stored neutrons. A study using finite element analysis of the possible pathways taken by the leakage currents is discussed. Similarly, background neutron counts may also lead to false EDM signals. But such backgrounds would also need to be correlated with the neutron spin state, high voltage state, LF signal, and spin-flipper states. We present a study here which constrains the false EDMs arising from such leakage currents to d^(False)_{n/Hg} < 4*10^{-28} e.cm, and from background asymmetries to d^(False)_{n-Backgrounds} < 3.6*10^{-65} e.cm.