First Experimental Limit on the Permanent Electric Dipole Moment of the Deuteron

TL;DR

This paper reports the first experimental limit on the deuteron EDM using storage ring techniques, demonstrating the potential for future charged hadron EDM searches.

Contribution

It presents the first measurement of the deuteron invariant spin axis in a magnetic storage ring and sets a new experimental limit on the deuteron EDM.

Findings

First experimental limit on deuteron EDM: |d^d|< 2.5×10^{-17} e·cm (95% C.L.)

Measured spin axis tilts of a few milliradians dominated by systematic effects

Demonstrated feasibility of storage ring methods for charged hadron EDM searches

Abstract

Permanent electric dipole moments (EDMs) provide a sensitive probe of physics beyond the Standard Model and are directly linked to additional sources of CP violation that could explain the matter-antimatter asymmetry of the universe. EDM measurements of charged particles in storage rings rely on detecting a small tilt of the invariant spin axis with respect to the ring plane. In this work, we present the experimental determination of the invariant spin axis of an ensemble of deuterons in the COoler SYnchrotron (COSY), a conventional magnetic storage ring, using a combination of a radio-frequency Wien filter, a superconducting Siberian snake and an electron-cooler solenoid. The measurements reveal tilts of a few milliradians, which are dominated by systematic effects. From the observed tilts, we derive the first experimental limit on the deuteron EDM, $|d^d|< 2.5\cdot10^{-17}\,e\cdot\mathrm{cm} \; (95\%\,\text{ C.L.})$. This result demonstrates the feasibility of using storage rings to search for EDMs of charged stable hadrons and provides a foundation for future dedicated facilities.