Speaker
Description
Dark photon is one of the candidates for cold dark matter, predicted by a part of string theories and high-scale inflation models. Dark photons interact with ordinary photons via tiny kinetic mixing with them. Owing to this interaction, the dark photons convert into millimeter-wave light at the electromagnetic boundaries, such as the surface of a metal plate. The frequency of the conversion photon corresponds to the mass of dark photon because of the energy conservation ($h\nu \simeq mc^2$); for example, a signal at 240 GHz corresponds to the mass of 1 $\text{meV}$. To detect the conversion photon from the dark photon in various frequency bands, we, the DOSUE-RR collaboration, have developed cryogenic millimeter-wave receivers. We have already performed the searches for conversion photons in the frequency range of 10–26.5 GHz. Since there is still an unexplored range up to $O$(100 GHz), we are focusing on the frequency range of 170–260 GHz as the next target. However, in this frequency range, there is no good low-noise amplifier to detect the tiny signal from the dark photons. To keep low noise, we installed a Superconductor-Insulator-Superconductor (SIS) mixer, which is commonly used in cutting-edge radio telescopes. This device allows us to down-convert the signal frequency from around 200 GHz to ~10 GHz, and to detect the signal with a low noise level of $< O\text{(100 K)}$. In this presentation, I will discuss the current status including receiver evaluation and future plans of the DOSUE-RR.
