The search for the neutron electric dipole moment at PSI

TL;DR

This paper reports the most sensitive measurement of the neutron electric dipole moment using ultracold neutrons at PSI, with future experiments planned to improve sensitivity and explore physics beyond the Standard Model.

Contribution

It presents the current best limit on the neutron EDM and introduces a new experiment, n2EDM, aiming to enhance measurement sensitivity by an order of magnitude.

Findings

Current limit: |d_n|<1.8×10⁻²⁶ e·cm at 90% CL

No evidence of nonzero neutron EDM found

Upcoming experiment aims to improve sensitivity tenfold

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) probes 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 ($|d_n|<1.8\times 10^{-26} \, e {\rm cm}$, C.L.90%). A new experiment designed to improve the sensitivity by an order of magnitude, n2EDM, is currently in construction.