Purity metrology closes on dark matter

Optical clocks are so accurate that it would take 20 billion years longer than the age of the universe – to lose or gain another. Now, the U.S. Researchers at the National Institute of Standards and Technology Jun Ji and the University of Colorado, led by Jun Ye, have used the precision and accuracy of their optical clock and the unprecedented stability of their crystalline silicon optical cavities to overcome any obstacles. Possible combination between the standard model of physics and the hitherto elusive component particles and fields of dark matter.

The existence of dark matter is indirectly evident from gravitational effects on the galactic and cosmological scales, but beyond that, little is known about its nature. One of the effects that emerges from the theoretical analysis of dark matter involving particles in the standard model of physics is the oscillation resulting in fundamental stability. Ye and colleagues discovered that if their world-class metrology equipment could not detect this oscillation, this apparently null result would be a useful confirmation that the strength of the interaction of dark matter with particles in the standard model of physics should also be less than determined. The record so far.

Stopping basic constant values

Previous attempts to bring down direct evidence of the Dark Matter range from laboratory experiments such as the Large Hadron Collider (LHC) to large particle collider projects. Many of these attempts have, for example, weakly interacted with International Particles (WIMP), consisting of a silver atom-like mass in the range of 100 g or so, a hypothesis designed to explain the elements of particle physics, and the theory of dark matter. Will sit off. Nevertheless, Ye and his colleagues used their optical clock and cavitation devices to detect possible interactions between dark matter and particles at the bottom of the mass spectrum below 1 EV, which is 500,000 times smaller than the mass of the remaining electrons. .

Optical clocks are a type of atomic clock. The first atomic clocks absorb hyperfin transitions in the molecule of cesium 133 – when the cesium 133 atom flips spin, the resulting change in the state of the molecule is emitted as electromagnetic radiation with a characteristic frequency in the microwave range. However, the transitions between the electron orbitals in the strontium molecule, with more corresponding frequencies corresponding to the ical optical range, lead to energy change, and now that technology has been developed to measure these transitions, it is also possible to maintain high-precision time. What’s more, the frequency of optical clocks is directly related to a certain basic stability, providing a way to measure the potential variability of this quantity with unprecedented accuracy.

Ye and his colleagues used their optical clock to find any difference in basic stability α, fine design, which defines the power of interaction between charged particles and photons. For this, they compare the frequencies of strontium molecules used in optical clocks with their crystalline silicon cavities, a device used in lasers that allow electromagnetic waves to bounce between reflected surfaces and create a steady wave with a characteristic frequency. The length of the cavity. The frequency of both the devices is determined in terms of both α and MM_E (Another basic constant that gives a set of electrons) but with different dependencies, so that the ratio between the two frequencies reveals any variation in the static any.

“People have used atomic clocks in microwave frequencies to limit the power of dark matter attachments, but this work will represent the first results of the use of optical atomic clocks to provide a barrier to the obscure signature of dark matter,” says Ye.

By comparing the frequency of the cavity with the clock molecules, the researchers compared it to the frequency of a hydrogen measure – a microwave frequency standard, which produces radiation based on transitions between different electronic and atomic spin states in a hydrogen atom. Although the hydrogen measure does not provide time to be as accurate as a strontium-based optical clock, it is based on energy transitions, which lead to a different relationship between frequency and stability α and m._e, Such that the ratio of the frequency of its crystalline silicon cavities provides probes for variations in its value._E, As well. When the oscillation at the value of સૂચ indicates the interaction between the dark matter and the electromagnetic field, the oscillation in m_E Will reveal the interaction with the electron mass.

The measured frequency ratio between both the cavity and the optical clock and the hydrogen measure also draws another crucial advantage – the stability of the crystalline silicon cavity. Colin Kennedy, a researcher at the group and the first author of a report on these results, explains that “most cavities are made of glass, which is an irregular, amorphous solid with a lot of rotation.” The cavity is composed of a large single crystal of silicon. “This new generation of cavities is made of single silicon crystals and is also kept at cryogenic temperatures, which makes them more stable in the order of magnitude. This is the main advantage of our work.”

Closed on dark matter

While (as expected) the researchers did not observe the oscillation in the basic conditions due to the interaction with the dark matter, their data narrowed the range of possible values ​​that could be the parameters of this interaction. For dark matter particles with masses in the range of 4.5 × 10¹⁶ 1 × 10 below¹⁹ EV, defined by the potential power of a dark object interaction, is restricted by a further factor of up to five by these results, and defined by m_E Restricted by a factor of 100 for people between 2 × 10¹⁹ And 2 × 10⁻²¹ EV.

“You first proposed the idea of ​​using optical cavity resonance frequency to compare atomic frequencies in an email exchange between me and Prof. Victor Flamm,” Yeh tells Phys.RG, recalling their exchange around 2015. The paper describing the basic ideas they discussed, Ye says, “wanted to see experimental results. And here we are.”

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