Demonstration of deuterium's enhanced sensitivity to symmetry violations governed by the Standard-Model Extension

TL;DR

This study used hyperfine spectroscopy of deuterium to set new, highly sensitive bounds on potential violations of CPT and Lorentz symmetry, surpassing previous hydrogen-based measurements by large margins.

Contribution

First constraints on certain Standard-Model Extension coefficients using deuterium spectroscopy, with improved bounds on spin-dependent coefficients and the most precise in-beam hyperfine splitting measurement.

Findings

Constraints on non-relativistic proton coefficients with k=2,4 are established for the first time.

Bounds on spin-dependent coefficients are significantly improved.

Deuterium hyperfine splitting measured with highest precision in-beam to date.

Abstract

We have performed hyperfine spectroscopy of two transitions in ground-state deuterium and searched for violations of \CPT and Lorentz symmetry that would manifest as sidereal variations of the observed transition frequencies. Several non-relativistic proton coefficients of the Standard-Model Extension framework have been addressed. The spin-independent coefficients with momentum power $k$=2,4 are constrained for the first time. Bounds on spin-dependent coefficients are improved by exploiting a sensitivity enhancement originating from the relative momenta of the nucleons in the deuteron. The best previous constraints by hydrogen maser measurements are surpassed by 4 and 14 orders of magnitude for coefficients with $k$=2 and 4, respectively. Furthermore, we find a deuterium zero-field hyperfine splitting of \SI{327.3843549(0.0000028)}{\mega \hertz}. This is in agreement with the literature and presents the most precise in-beam measurement of this quantity.