Search for physics beyond the standard model with highly charged ions

Introduction

Spectroscopy has been a central tool in modern physics: it has helped us understand atomic structure, the expansion of the universe, and the composition of exoplanet atmospheres. Today, high-precision spectroscopy is one of the most promising tools for investigating some of the most fundamental open questions. Many theories beyond the standard model of particle physics can be tested by detecting tiny changes in atomic transition frequencies caused by the interaction with new particles, new forces, or the variation of fundamental constants.

Target of Investigation

An especially attractive target is the search for temporal or spatial variations of the fine-structure constant, which is predicted by several different theories. Highly-charged ions (HCIs) are especially well suited for this search, as they have transitions that are over an order of magnitude more sensitive to the fine-structure constant than most other atomic systems.

Methodology

The precision necessary for these measurements will soon be within reach, thanks to recent demonstrations of sympathetic cooling and quantum-logic spectroscopy of HCIs. I propose an experiment that simultaneously probes two of the most sensitive transitions in HCIs using quantum logic spectroscopy and directly compares their transition frequencies.

Advantages of the Proposed Method

This method doubles the advantage of their enhanced sensitivities and reduces systematic effects introduced by an indirect comparison via the SI second standard. Together, these gains will allow an improvement of over two orders of magnitude on current bounds on the temporal variation of the fine-structure constant.

Further Investigations

I will also take advantage of the exotic nature of these extreme atoms to test further theories of fundamental physics. In particular, I plan to exploit their enhanced Rutherford scattering cross section to determine an improved limit on the number density of proposed millicharged dark matter particles.

Conclusion

This data will help narrow down the most viable theories for physics beyond the standard model.