Search for dark photon using a millimeter-wave spectrometer in the unexplored mass range

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14486
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Kyoto University (2021-2022); The University of Tokyo (2020)
• Principal Investigator: Adachi Shunsuke 京都大学, 白眉センター, 特定助教 (80835273)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 暗黒光子 / ダークマター / ミリ波

Outline of Final Research Achievements

Dark matter occupies a quarter of the total energy in the universe. However, we don't know the mass. This research aims to detect dark matter using a millimeter-wave spectrometer to reveal its characteristics. In particular, our target is a "dark photon" which is predicted to convert to a millimeter-wave and the frequency corresponds to a mass of dark matter. Since the dark matter mass is unknown, the broadband search of the millimeter-wave signal is required.
We have developed a millimeter-wave spectrometer for the frequency range of 18--26.5 GHz and conducted a search for the signal from the dark photon. We have not found any sign of the dark photon, but we achieved exploring the dark photon with much higher sensitivity than the conventional constraints from the cosmic observations. In the final year, we also searched for the dark photon in the frequency range of 10-18 GHz with another developed spectrometer.

Free Research Field

素粒子物理学

Academic Significance and Societal Importance of the Research Achievements

暗黒光子をミリ波帯域で広く探索した実験は今までになく、ミリ波分光器を用いた暗黒光子探索の手法の確立が本研究によっておこなえたといえる。また、暗黒光子の発見には至らなかったが、今回探索した10ー26.5 GHzに対応する質量領域(0.04ー0.11ミリ電子ボルト)では暗黒光子が存在している可能性が低いという知見が得られた。今後、本研究で確立した手法をもとに、より広い周波数帯域、すなわち質量領域での暗黒光子ダークマターを探索していきたい。