Electric dipole moments (EDMs) of elementary particles violate time-reversal symmetry. According to
the CPT theorem, this also implies the violation of combined charge-conjugation and parity-inversion
(CP) symmetry, making EDMs powerful tools for probing physics beyond the current Standard Model
(SM) of particle physics.
The muEDM experiment aims at setting the ground for a new direct electric dipole moment (EDM)
search using muons. The experiment will perform this dedicated search using the frozen-spin technique
for the first time worldwide, aiming at improving the current sensitivity by more than three orders of
magnitude to better than 6 × 10−23 e cm, an astonishing jump. This search is a unique opportunity
to probe previously uncharted territory and to test theories Behind Standard Model physics.
The experiment will be performed in two phases.
Phase I: In this exploratory phase, we will set up an experiment to demonstrate the frozen-spin
method and search for a muon EDM using an existing solenoid. The instrument will be connected
to a surface-muon beamline at PSI, delivering about 4e6 s−1 muons at a momentum of p=28
MeV/c in a transverse phase space of ϵxx′ = 192 πmmmrad and ϵyy′ = 171 πmmmrad. Although
the sensitivity to a muon EDM will be sufficient to improve the current best measurement, the
main purpose is to establish all necessary techniques and methods for a measurement with the
highest possible sensitivity.
Phase II: The future instrument will use a dedicated magnet with minimal field gradient between
injection and storage region to increase the acceptance phase space and integrate all lessons
learned from Phase I. In addition, it will benefit from being coupled to the highest-intensity
muon beam at PSI, with more than 1e8 s−1 muons at a momentum of p=125 MeV/c in a
transverse phase space of ϵxx′ = 920 πmmmrad and ϵyy′ = 213 πmmmrad.
In this seminar we will review the motivation to search for EDMs and the current status of the
muEDM experiment at PSI.
