The search for the neutron electric dipole moment at PSI

Abstract

The existence of a nonzero permanent electric dipole moment (EDM) of the neutron would reveal a new source of CP violation and shed light on the origin of the matter–antimatter asymmetry of the Universe. The sensitivity of current experiments using stored ultracold neutrons (UCN) probe new physics beyond the TeV scale. Using the UCN source at the Paul Scherrer Institut, the nEDM collaboration has performed the most sensitive measurement of the neutron EDM to date, still compatible with zero (|d_n|<1.8\times 10^{-26} \, e {cm}|dn|<1.8×10−26ecm, C.L.,90%). A new experiment designed to improve the sensitivity by an order of magnitude, n2EDM, is currently under construction.

UCN, the ultracold neutron source -- neutrons for particle physics

“…• new limits for mirror-neutron oscillations in mirror magnetic fields [35]. Some of these results are treated in Section 18 [36] and Section 19 [37] of this volume.…”

Global Constraints on Yukawa Operators in the Standard Model Effective Theory

“…e simplest hadronic system used in our t is the neutron. e most recent experimental bound on the neutron EDM is [36] |d n | < 1.8 × 10 −26 e cm @ 90% CL .…”

“…e future projections estimate an improvement of the limit to |d n | < 10 −27 e cm [36]. roughout this work, we assume that the θ QCD term has negligible e ect on any EDMs and all e ects arise from the Yukawa SMEFT operators.…”

Indirect searches for dark matter with the nEDM spectrometer

“…An important feature of the nEDM spectrometer [1] is the mercury co-magnetometer. The search for the neutron electric dipole moment employs the ratio R of the neutron precession frequency ( f n ) to the mercury one ( f Hg ) using the fact that this ratio is, to first order, free from magnetic field fluctuations.…”

“…Apart from searching for the electric dipole moment of the neutron, the nEDM apparatus at PSI (Section 27 [1]) is also an excellent tool to search for signatures of dark matter particles. The first potential signature studied was a high precision measurement of the shift in the ratio of the spin-precession frequencies of ultracold neutrons (UCN) and 199 Hg atoms.…”