31 January 2020
The theory of General Relativity is currently challenged by theoretical considerations and by galactic and cosmological observations, where new fields, in addition to the space-time metric, are introduced to model the gravitational interaction. Some galactic and cosmological observations are explained by the introduction of cold Dark Matter and of Dark Energy. Little is currently known about these two components that constitute the major part of our Universe, and numerous laboratory searches are aiming at a direct detection and characterization of Dark Matter.
Physicists at SYRTE have used six years of accurate hyperfine frequency comparison data of the dual Rubidium and Caesium cold atom fountain clock FO2 to search for a massive scalar dark matter candidate. Such a scalar field is expected to oscillate at a frequency proportional to its mass, and can induce harmonic variations of the fine structure constant, of the mass of fermions and of the quantum chromodynamic mass scale, which will directly impact the Rubidium/Caesium hyperfine transition frequency ratio. We find no signal consistent with a scalar dark matter candidate but provide improved constraints on the coupling of the putative scalar field to standard matter. Our limits are complementary to previous results that were only sensitive to the fine-structure constant, and improve them by more than an order of magnitude when only a coupling to electromagnetism is assumed. The figure below shows on a log scale the excluded values of the putative coupling constants between dark matter and electromagnetism and/or the atomic nucleus as a function of dark matter mass.
- Estimated values of the linear combination of coupling constants between a massive scalar field and standard matter fields as a function of scalar field mass. The best fit values are shown in blue, with the 95% confidence upper bounds in red. The purple dashed line represents the 95% confidence upper bound obtained previously with Dy atoms only sensitive to .
Read the article in Physical Review Letters
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