Searching for dilaton dark matter with atomic clocks (1405.2925v2)

Abstract: We propose an experiment to search for ultralight scalar dark matter (DM) with dilatonic interactions. Such couplings can arise for the dilaton as well as for moduli and axion-like particles in the presence of CP violation. Ultralight dilaton DM acts as a background field that can cause tiny but coherent oscillations in Standard Model parameters such as the fine structure constant and the proton-electron mass ratio. These minute variations can be detected through precise frequency comparisons of atomic clocks. Our experiment extends current searches for drifts in fundamental constants to the well-motivated high-frequency regime. Our proposed setups can probe scalars lighter than 10^-15 eV with discovery potential of dilatonic couplings as weak as 10^-11 times the strength of gravity, improving current equivalence principle bounds by up to 8 orders of magnitude. We point out potential 10^4 sensitivity enhancements with future optical and nuclear clocks, as well as possible signatures in gravitational wave detectors. Finally, we discuss cosmological constraints and astrophysical hints of ultralight scalar DM, and show they are complimentary to and compatible with the parameter range accessible to our proposed laboratory experiments.

• The paper introduces a novel method for detecting ultralight dilaton dark matter using the precision of atomic clocks.
• It employs advanced frequency metrology and inter-element clock comparisons to achieve sensitivity improvements by several orders of magnitude.
• The findings offer actionable insights into testing fundamental physics and probing dark matter interactions beyond traditional equivalence principle tests.

Overview of "Searching for Dilaton Dark Matter with Atomic Clocks"

The paper "Searching for Dilaton Dark Matter with Atomic Clocks" explores the potential interaction between ultralight scalar dark matter and Standard Model particles, specifically focusing on dilaton-like couplings. The authors propose innovative experimental methods to detect these interactions using the precision of atomic clock technologies. This research presents a novel approach to probing dilaton dark matter, expanding the parameter space explored by existing methods such as equivalence principle (EP) tests.

Theoretical Background and Motivation

In the context of string theory and other beyond Standard Model frameworks, dilatons and similar particles such as moduli and axion-like particles emerge as compelling candidates for dark matter (DM). The ultralight scalar dark matter hypothesized in this paper is predicted to induce minute oscillations in the fundamental constants of nature, including the fine-structure constant and various mass ratios. The theoretical motivation for such research stems from the lack of concrete evidence for new physics at the electroweak scale and the continued mystery surrounding dark matter's nature.

Experimental Proposal

The authors suggest utilizing the sensitivity of atomic clocks to detect oscillations in the constants mentioned. By leveraging the advancements in frequency metrology, specifically the precision of frequency combs and optical clocks, they seek to observe any variations in the frequency ratios of atomic transitions. The experimental setup involves comparing clocks based on different elements, as these clocks exhibit different dependencies on the constants in question. This allows for the detection of oscillatory effects attributable to dilaton DM couplings.

Sensitivity and Comparisons

The proposed experimental methodology is poised to improve the detection sensitivity for dilatonic couplings by several orders of magnitude compared to current EP test methods. By monitoring intricate variations in atomic transition frequencies, the experiment can explore scalar dark matter with masses lighter than $10^{-15}$. The authors anticipate up to a $10^4$-fold sensitivity enhancement with further advancements in clock technology, such as with next-generation optical and potential nuclear clocks.

Implications and Future Directions

The theoretical implications of successfully detecting these oscillations would provide direct evidence for the existence of ultralight scalar dark matter, offering insights into string theory vacua and the coupling mechanisms of fundamental forces. Moreover, evaluating violations of the equivalence principle through gravitational interactions could elucidate hidden sectors in particle physics and cosmology. The authors also speculate on the potential of gravitational wave detectors to contribute complementary sensitivity, further broadening the horizon of experimental techniques in probing dark matter.

Conclusion

By marrying theoretical predictions with high-precision atomic clock experiments, this paper charts a promising path toward understanding dark matter's scalar components. It underscores the importance of exploring non-traditional experimental avenues to answer some of the most persistent puzzles in contemporary physics. The authors' proposal represents a significant step in combining theoretical models with cutting-edge technology, paving the way for future discoveries at the intersection of particle physics and cosmology.