A brand new method could help scientists make clear the universe’s most mysterious substance by narrowing down the hunt for a specific dark matter candidate — hidden “dark photons.”
Dark matter comprises around 85% of the matter content of the universe, yet since it doesn’t interact with light or does so only very weakly, it stays effectively invisible. The indisputable fact that dark matter doesn’t appear to interact electromagnetically means scientists know it might probably’t be made up of the atoms that comprise the “normal” matter that makes up stars, planets and our bodies.
The mystery of dark matter is such a pressing problem for scientists since it means the matter we see comprises just 15% of the stuff, not including energy, within the cosmos. This has led to the seek for potential dark matter candidates, equivalent to so-called “hidden” or “dark” photons.
These dark photons would differ from odd photons, that are massless particles that make up light, as dark photons are theorized to own mass. The mass of dark photons could be tiny, nonetheless, at around twenty orders of magnitude lower than the mass of an electron. It is that this ultralight nature that makes dark photons a superb candidate for dark matter and would also make them incredibly tough to detect.
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Dark photons were initially suggested as a dark matter candidate because, theoretically, they might weakly interact with odd photons, meaning they may have played a task in heating up the early universe. This motion would explain why the cosmic web, a large-scale structure within the universe linking together galaxies, was hotter than predicted when observed by the Hubble Space Telescope.
Now, researchers from the California Institute of Technology (Caltech) have provide you with a brand new detection method for dark photons. And while this recent strategy hasn’t yet turned up any of the hypothetical particles, it has placed constraints on their characteristics, which can aid future searches.
“The sensitivity of a hidden photon dark matter experiment is determined by the strength of the dark matter signal in comparison with the smallest signal you’ll be able to detect,” team member Nikita Klimovich, a researcher in Oxford University’s Department of Physics, told Phys.org.
“For hidden photon searches, the amplitude of the dark matter signal scales with the realm of the metal dish used, while the minimal detectable signal level is essentially determined by the noise level [the interference] of the amplifiers used to read out the antenna,” Klimovich added.
An ultracool dark matter hunt
The inspiration for the team’s dark photon search comes from a previous try and hunt for hidden dark matter called the SHUKET experiment, which uses an electromagnetic telescope.
“Previous searches that inspired this work, just like the SHUKET experiment, generally aimed to maximise the signal strength through having a really large dish while using the perfect commercially available low-noise amplifiers that they had access to,” Klimovich explained.
The team took a unique approach in the brand new study, nonetheless, using quantum-limited amplifiers moderately than off-the-shelf amplifiers and conducting their dark photon hunt at incredibly low temperatures. They searched at temperatures between minus 459 degrees Fahrenheit (minus 272.9 degrees Celsius) and minus 459.6682 degrees F (minus 273.149 degrees C), only a fraction of a level warmer than the coldest temperature theoretically possible, absolute zero.
While this allowed the scientists to significantly reduce the minimal signal levels they may detect in comparison with other experiments using off-the-shelf tech, it got here with a serious drawback. The small vacuum-insulated environment of the cryostat device the scientists used to chill their apparatus severely limited the scale of the spherical metallic dish they may use of their search.
Though this meant a much lower signal than that detected by SHUKET and other dark matter hunting experiments, the team hoped that this drawback could be offset by the increased sensitivity of the measurements they collected.
“If a hidden photon existed with a mass corresponding to the frequency range we were sensitive to, we should always see a small excess lump of power coming from the dish in comparison with the reference,” Klimovich said. “Because we saw no such signal, we could set a brand new upper limit on the coupling of such a hidden photon particle to the electromagnetic field based on the smallest signal level we’d have been capable of detect.”
While the signal of dark photons wasn’t present within the team’s measurement, the approach taken by the scientists has placed stringent recent constraints on theoretical hidden photons. Because the seek for dark matter candidates continues, these constraints and this recent approach could eventually play a task in the invention of dark photons and, thus, in solving the dark matter mystery.
“Apart from the brand new limits set on detection, we have now demonstrated a really accessible approach for hidden photon experiments in the long run,” Klimovich concluded.
The team’s research was published last month within the journal Physical Review Letters.