Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

TL;DR

This study explores the feasibility of using a storage ring to detect electric dipole moments in charged particles, aiming for extremely sensitive measurements while managing systematic errors through advanced polarization control.

Contribution

It proposes a novel storage ring method for measuring particle EDMs with high sensitivity and outlines a stepwise experimental plan to demonstrate technical feasibility and precision.

Findings

Achieved reduced polarization measurement errors

Demonstrated long polarization lifetimes in the horizontal plane

Controlled polarization direction via feedback from scattering measurements

Abstract

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly $^3$He) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation from the longitudinal to the vertical direction. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. A stepwise plan is foreseen, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal plane polarization lifetimes, and control of the polarization direction through feedback from scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally a high-precision electric-field storage ring.