Researchers at JILA have used the most advanced atomic clock to narrow the search for the elusive dark matter. This is an example of the ever-improving timepiece that has value beyond timekeeping.
Earlier atomic clocks operating at microwave frequencies have been looking for dark matter before, but this is the first time that newer atomic clocks operating at higher optical frequencies and ultra-stable oscillators that ensure stable light waves are used to set more precise boundaries. on.The study is described in Medical letter .
Astrophysics observations show that dark matter constitutes most of the “matter”
It is expected that ultralight dark matter will produce small fluctuations in two basic physical “constants”: electronic mass and fine structure constant. The JILA team used a strontium lattice clock and a hydrogen maser (a microwave version of a laser) to compare its well-known optical and microwave frequencies with the frequency of light that resonates in an ultra-stable cavity made of single crystals. Pure silicon. The resulting frequency ratio is sensitive to changes in the two constants over time. The relative fluctuations of ratios and constants can be used as sensors to connect the cosmological model of dark matter with accepted physical theories.
The JILA team has set a new limit for “normal” fluctuations on the floor. If this limit is exceeded, any abnormal signals found in the future may be caused by dark matter. The researchers limited the coupling strength and fine structure constant of ultralight dark matter to electronic mass to 10 orders of magnitude.-5 Or smaller, the most accurate measurement of this value.
JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.
NIST/JILA researcher Jun Ye said: “No one actually knows what concentration of dark matter you will see in laboratory measurements.” “The problem is that the physics we know is not very complete at this point. We know that. Something is missing, but we don’t yet know how to solve it.”
Ye added: “We know the existence of dark matter from astronomical observations, but we don’t know how dark matter relates to ordinary matter and the values we measure.” “Experiments like ours allow us to test people’s attempts to explore the nature of dark matter. Various theoretical models. By setting better and better boundaries, we hope to eliminate some incorrect theoretical models and eventually discover them later.”
Ye said that scientists are not sure whether dark matter consists of particles or oscillating fields that affect the local environment. He said that the JILA experiment aims to detect the “pull” effect of dark matter on ordinary matter and electromagnetic fields.
Atomic clocks are the main detectors of dark matter because they can detect changes in fundamental constants and are rapidly improving in accuracy, stability and reliability. The stability of the cavity is also a key factor in the new measurement. The resonant frequency of light in a cavity depends on the length of the cavity, which can be traced back to the Bohr radius (the physical constant is equal to the distance between the nucleus and the electron in a hydrogen atom). The Bohr radius is also related to the value of the fine structure constant and electronic mass. Therefore, compared with the transition frequency in atoms, changes in resonance frequency can indicate fluctuations in these constants caused by dark matter.
The researchers collected 12-day strontium/cavity frequency ratio data with the clock running 30% of the time, and the data set was 978,041 seconds long. The hydrogen maser data spans 33 days, of which maser runs 94% of the time, resulting in a record of 2,826,942 seconds. The hydrogen/cavity frequency ratio provides useful sensitivity to electronic mass, although masers are not as stable as strontium clocks and produce noisier signals.
Researchers at JILA collected dark matter search data in a recent improved timescale demonstration. The system integrates data from multiple atomic clocks to generate a single highly accurate timing signal for distribution. With the improvement of atomic clock performance, optical cavity and time scale, the frequency ratio can be rechecked with higher resolution in the future, thus further expanding the range of dark matter search.
Ye said: “As long as you run an optical atomic time scale at any time, you have the opportunity to set a new limit or discover dark matter.” “In the future, when we can put these new systems into orbit, it will become a search for The largest’telescope’ built from dark matter.”
Precision measurement technology can solve dark matter
Priscilla Chan optical clock joined the pursuit of dark matter, physical (2020). DOI: 10.1103 / Physics.13.s145
Colin J. Kennedy et al. The combination of precision metrology and cosmology: Through the comparison of atomic cavity frequency, the constraint on ultra-light dark matter is improved, Medical letter (2020). DOI: 10.1103 / PhysRevLett.125.201302
Provided by the National Institute of Standards and Technology
Citation: Advanced atomic clocks make better dark matter detectors (November 12, 2020) From November 12, 2020 from https://phys.org/news/2020-11-advanced-atomic-clock-dark-detector .html search
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