A new method could help scientists shed light on the universe’s most mysterious matter and narrow down the search for hidden “dark photons,” a specific dark matter candidate.

Dark matter makes up about 85% of the matter in the universe, but remains virtually invisible because it does not interact or interact very weakly with light. The fact that dark matter does not interact electromagnetically means that scientists know it cannot be made from the atoms that make up the “normal” matter that makes up stars, planets, and our bodies.

The mystery of dark matter is a very urgent problem for scientists because it means that the matter we see in space makes up only 15% of matter, excluding energy. This has led to the search for potential dark matter candidates, such as so-called “hidden” or “dark” photons.

These dark photons will differ from ordinary photons, which are massless light-producing particles, because dark photons theoretically have mass. However, the mass of dark photons would be very small, about twenty times less than the mass of an electron. It is this ultralight nature that makes dark photons good candidates for the dark matter role and also makes them incredibly difficult to detect.

Dark photons were originally proposed as dark matter candidates because, in theory, they interact weakly with ordinary photons, meaning they could play a role in warming the early universe. This action may explain why the cosmic web, a large-scale structure that connects galaxies in the universe, is hotter than predicted during observations by the Hubble Space Telescope.

Now researchers from the California Institute of Technology (Caltech) have invented a new method for detecting dark photons. And while this new strategy has yet to detect any of the hypothetical particles, it does place constraints on its properties that will aid future searches.

“The sensitivity of the latent photon dark matter experiment depends on the strength of the dark matter signal compared to the smallest signal you can detect,” said team member Nikita Klimovich, a research associate in Oxford University’s Department of Physics. He told Phys.org.

“To search for hidden photons, the amplitude of the dark matter signal depends on the area of ​​the metal plate used, while the minimum detectable signal level is largely determined by the noise level. [перешкод] amplifiers used to read the antenna, Klymovych added.

The hunt for ultra-cold dark matter

The inspiration for the team’s search for dark photons comes from a previous attempt to hunt for hidden dark matter, called the SHUKET experiment, which uses an electromagnetic telescope.

“Previous research that inspired this work, such as the SHUKET experiment, was generally aimed at maximizing signal strength with a very large antenna using the best commercially available low-noise amplifiers they had access to,” Klimowicz said.

In the new study, however, the team took a different approach, using quantum-limited amplifiers instead of standard amplifiers and hunting dark photons at incredibly low temperatures. They searched just one degree above absolute zero, the theoretically lowest temperature possible, ranging from minus 459 degrees Fahrenheit (minus 272.9 degrees Celsius) to minus 459.6682 degrees Fahrenheit (minus 273.149 degrees Celsius).

While this allowed the scientists to significantly lower the minimum signal level they could detect compared to other experiments using off-the-shelf technology, it had a major drawback. The small, vacuum-insulated environment of the cryostat that the scientists used to cool their device severely limited the size of the spherical metal bowl they could use during the search.

While this meant a much lower signal than that found by SHUKET and other experiments investigating dark matter, the team hoped that this shortcoming would be compensated for by the increased precision of the measurements they collected.

“If there is a latent photon with a mass corresponding to the frequency range to which we are sensitive, we should see a small excess of power coming from the dish compared to the reference,” Klimowicz said. Said. “Since we have not seen such a signal, we were able to set a new upper limit for the binding of such a latent photon particle to the electromagnetic field, based on the smallest signal level we could detect.”

Despite the lack of a dark photon signal in the team’s measurements, the approach the scientists used placed strict new restrictions on theoretically hidden photons. As the search for dark matter candidates continues, these constraints and this new approach may eventually play a role in discovering dark photons and thus unraveling the mystery of dark matter.

“Besides the new frontiers placed on detection, we have demonstrated a very accessible approach for future stealth photon experiments,” Klimowicz said. Source