In recent years, physicists have developed an interest in the concept of ultralight dark matter, which proposes that dark matter is composed of bosons with extremely low masses. One such candidate is the “dark photon,” which is predicted to interact weakly with matter by coupling to regular photons through a process known as kinetic mixing.
Now, Haipeng An and colleagues at China’s Tsinghua University propose that radio telescopes may be able to detect dark photons through their interactions with unbound electrons. Using data from China’s Five-hundred-meter Aperture Spherical Telescope (FAST), An and associates established a maximum probability for such interactions.
Searching for uncommon dark photon-regular matter interactions constrains lightweight dark matter.
At dish-shaped radio telescopes such as FAST, incoming radio waves excite electron oscillations, producing a reflected signal that is detected by the telescope’s central receiver. If dark photons interact with unbound electrons in the dish through kinetic mixing, they should also generate electromagnetic waves with a frequency dependent on the mass of the dark photons.
The signature of this interaction should, in theory, be detectable within the overall radio signal captured by the telescope. FAST’s observations in the frequency range of 1–1.5 GHz were analyzed for indications of kinetic mixing by A and coworkers. Finding no such signature, they conclude that the dimensionless value that quantifies the kinetic mixing rate cannot exceed 1012.
In addition to using extant FAST data, the researchers projected dark-photon detection sensitivity using the Low-Frequency Array in Europe and the upcoming Square Kilometre Array in Australia and South Africa. Following this, they plan to analyze data from space-based radio telescopes, which are sensitive to dark-photon-induced signals at frequencies lower than those accessible to terrestrial radio telescopes.