A Storage Ring proton Electric Dipole Moment experiment: most sensitive experiment to CP-violation beyond the Standard Model

TL;DR

This paper proposes a highly sensitive storage ring experiment to measure the proton electric dipole moment, aiming to detect CP-violation beyond the Standard Model with unprecedented precision.

Contribution

It introduces a detailed design for a storage ring proton EDM experiment achieving 10^{-29} e·cm sensitivity, including innovative methods for spin coherence and electric field application.

Findings

Feasibility demonstrated through spin coherence and electric field studies

Design achieves the targeted sensitivity level

Future upgrades could improve sensitivity by an order of magnitude

Abstract

The Storage Ring EDM Collaboration is completing a comprehensive proposal to DOE for a sensitive proton EDM experiment at the 10-29e\cdot cm level. This involves building an electric ring of radius R~40 m, with bending provided by stainless steel plates separated by 3 cm gap, providing an electric field of 10 MV/m. This ring can store protons of 0.7 GeV/c momentum, also known as "magic" due to the unique property that the spin and momentum vectors precess at the same rate in any electric field. If the spin is kept longitudinal for most of the duration of the storage time, the radial E-field acts on the proton electric dipole moment and can cause a measureable vertical spin precession. Studies on spin coherence time, on the polarimeter system, and the electric field show that we can reach the experimental goals. A plan on the relative beam position monitors uses currently available technology and applies it in an accelerator environment. Some R&D is needed to establish the feasibility of the plan. Prospects of further improvement with a future upgrade for another order of magnitude in the EDM sensitivity are also laid out.