Dark matter, which constitutes over 80% of all matter, is known to only have gravitational interactions with observable matter according to astronomical observations. A team at PTB utilized highly sensitive atomic clocks to investigate the possibility of ultralight dark matter influencing the fine-structure constant but found no significant alterations, thereby enhancing our comprehension of its probable interactions and the constant’s temporal stability.
The comparison of optical clocks at PTB supports the ongoing mission to uncover potential connections between ultralight dark matter and photons.
In the field of astronomy, observations point to the existence of “dark matter,” making up over 80% of all matter. Current knowledge suggests that its primary interaction with visible matter is gravitational. Remarkably, no proven evidence exists that it communicates with photons, the elementary particles that form light as well. This non-interaction is why the term “dark” is applied. Both the composition of dark matter and any possible unknown engagements with ordinary matter persist as captivating mysteries.
A promising theoretical concept hints that dark matter might be composed of exceptionally lightweight particles, behaving more like waves than distinct particles – referred to as “ultralight” dark matter. Under this assumption, weak, previously unexplored interactions between dark matter and photons might cause minute fluctuations in the fine-structure constant.
The fine-structure constant is a vital constant characterizing the intensity of electromagnetic interaction, governing atomic energy scales and impacting the reference transition frequencies in atomic clocks. As various transitions have different sensitivities to changes in the constant, atomic clock comparisons can aid in the search for ultralight dark matter. PTB’s researchers employed an especially sensitive atomic clock to explore possible alterations to the fine-structure constant in this quest.
This specific clock was matched with two other less sensitive atomic clocks in a series of month-long measurements. Analysis of the collected data for any oscillations, indicative of ultralight dark matter, revealed no significant findings, leaving dark matter “dark” even after thorough examination.
The quest to detect elusive dark matter was not successful. The lack of a signal led to the establishment of new upper bounds on the strength of any potential ultralight matter coupling to photons, improving the existing limits by more than tenfold across a broad spectrum.
Additionally, the team investigated whether the fine-structure constant might slowly change over time, but no such variation was found in the data. Existing boundaries were also reinforced, implying the constant’s enduring stability over extended durations.
A departure from past clock comparisons, two of the three atomic clocks in this study were contained within a single experimental system. By using two varying transition frequencies of a lone trapped ion, the researchers achieved this. This advancement represents a significant stride toward making optical frequency comparisons more streamlined and resilient – such as for potential space-based searches for dark matter.
Reference: “Improved Limits on the Coupling of Ultralight Bosonic Dark Matter to Photons from Optical Atomic Clock Comparisons” by M. Filzinger, S. Dörscher, R. Lange, J. Klose, M. Steinel, E. Benkler, E. Peik, C. Lisdat, and N. Huntemann, 22 June 2023, Physical Review Letters.
DOI: 10.1103/PhysRevLett.130.253001
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Frequently Asked Questions (FAQs) about fokus keyword: dark matter
What were the researchers at PTB investigating about dark matter?
The researchers at PTB were using sensitive atomic clocks to investigate the possible interactions of ultralight dark matter with the fine-structure constant. They were seeking evidence of such dark matter affecting the constant, but found no significant changes, thus refining the understanding of potential interactions and the stability of the fine-structure constant over time.
What is the fine-structure constant, and why is it important in this study?
The fine-structure constant is the natural constant that describes the strength of the electromagnetic interaction. It determines atomic energy scales and influences transition frequencies used as references in atomic clocks. In this study, it was important because variations in the fine-structure constant might indicate interactions with ultralight dark matter.
Why is dark matter termed “dark,” and what does the study reveal about it?
Dark matter is termed “dark” because, to our current understanding, it primarily interacts with visible matter through gravitational forces, with no established evidence that it interacts with photons, the particles that form light. This study further emphasizes that dark matter remains “dark,” as no significant interactions with photons or changes in the fine-structure constant were detected.
How did the researchers use atomic clocks in their investigation?
The researchers used highly sensitive atomic clocks to look for potential interactions between ultralight dark matter and the fine-structure constant. They compared different atomic clocks over months-long measurements and analyzed the data for oscillations, which would be the signature of ultralight dark matter. No significant oscillations were found.
What are the implications of the research findings?
The research findings have refined our understanding of dark matter by not detecting significant interactions with the fine-structure constant, thereby setting new experimental upper limits on the strength of a possible coupling of ultralight matter to photons. The absence of variation in the fine-structure constant also indicates that it remains stable over long periods. These results aid in the ongoing quest to unravel the mysteries of dark matter.
