A compact frozen-spin trap for the search for the electric dipole moment of the muon

TL;DR

This paper proposes a compact frozen-spin trap design for measuring the muon's electric dipole moment, aiming to improve sensitivity and test fundamental symmetries in particle physics.

Contribution

It introduces a novel conceptual design for a muon EDM search using the frozen-spin technique in a compact trap, with detailed sensitivity estimates for future experiments.

Findings

Expected sensitivity of 4E-21 ecm in Phase I

Projected sensitivity of 6E-23 ecm in Phase II

Design outlined for a demonstration experiment at PSI

Abstract

The electric dipole moments~(EDM) of fundamental particles inherently violate parity~(P) and time-reversal~(T) symmetries. By virtue of the CPT theorem in quantum field theory, the latter also implies the violation of the combined charge-conjugation and parity~(CP) symmetry. We aim to measure the EDM of the muon using the frozen-spin technique within a compact storage trap. This method exploits the high effective electric field, \$E \approx 165\$ MV/m, experienced in the rest frame of the muon with a momentum of about 23 MeV/c when it passes through a solenoidal magnetic field of \$|\vec{B}|=2.5\$ T. In this paper, we outline the fundamental considerations for a muon EDM search and present a conceptual design for a demonstration experiment to be conducted at secondary muon beamlines of the Paul Scherrer Institute in Switzerland. In Phase~I, with an anticipated data acquisition period of 200 days, the expected sensitivity to a muon EDM is 4E-21 ecm. In a subsequent phase, Phase~II, we propose to improve the sensitivity to 6E-23 ecm using a dedicated instrument installed on a different beamline that produces muons of momentum 125 MeV/c}.