Approaching the mystery of dark matter: Recording its gravitational effects on visible matter

Thinking big and dark by starting small and light.

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Instead of observing the dark matter directly, scientists have approached the dark matter mystery by recording its gravitational effects on visible matter. Using technology for millimeter-wave sensing under cryogenic settings, typified by low thermal noise, a team of researchers at Kyoto University has now developed an experimental technique for analyzing ultra-light dark matter in the range of 0.1 millielectron volts.

Lead author Shunsuke Adachi said, “We achieved experimental parameters for the unexplored mass range of dark photon dark matter — or DPDM — by using new techniques previously untested in this field.”

Thermal noise is reduced in a specialized millimeter-wave receiver by cooling it to -270 °C to handle weak conversion photons. With a mass range of roughly 0.1 meV, this cryogenic receiver is used to look for DPDMs.

Adachi asserts that even though his team failed to detect any meaningful signal in this dataset, they nevertheless created new avenues for the study of dark matter by executing their tests under more stringent restrictions than cosmic ones.

Theoretically, dark photons can be transformed into common photons utilizing metal plate surfaces. According to energy conservation, these conversion photons match the mass of dark photons. For instance, the dark photon group range of 0.05 to 1 meV corresponds to the conversion photon frequency of 10-300 GHz.

Adachi said, “We are thrilled that our small team were able to obtain important results from our high-sensitivity experiments for detecting DPDMs in an unexplored mass range.”

Journal Reference:

  1. S. Kotaka, S. Adachi, R. Fujinaka, S. Honda, H. Nakata, Y. Seino, Y. Sueno, T. Sumida, J. Suzuki, O. Tajima, S. Takeichi (2023). Search for Dark Photon Dark Matter in the Mass Range 74-110 μeV with a Cryogenic Millimeter-Wave Receiver. Physical Review Letters, 130(7):071805. DOI 10.3847/2041-8213/acb25e

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