Cosmological Evolution and Search for Light New Particles with Ultraweak Interactions

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H02875
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Tohoku University
• Principal Investigator: Takahashi Fuminobu 東北大学, 理学研究科, 教授 (60503878)
• Co-Investigator(Kenkyū-buntansha): 石渡 弘治 金沢大学, 数物科学系, 准教授 (40754271) ; 横崎 統三 東北大学, 理学研究科, 助教 (80779322)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: ダークマター / 初期宇宙

Outline of Final Research Achievements

We have proposed new cosmological evolution and production process of the weakly interacting slim particles. As a representative result, we proposed a new production mechanism by axions in the scenario where dark photons become dark matter. In particular, it was found that dark photons with extremely low masses, which were difficult to produce, can become cold dark matter. We also find that the cosmological upper bound on the axion decay constant is relaxed significantly by considering the stochastic dynamics of the QCD axion during inflation.

Free Research Field

素粒子論的宇宙論

Academic Significance and Societal Importance of the Research Achievements

この宇宙に遍在するダークマターやダークエネルギーの候補である粒子に関して，その宇宙論的な進化および生成過程について詳細に調べることによって，新たに尤もらしい質量領域や将来実験におけるパラメタ－領域を発見することができた。このような新粒子として，ダークフォトンやアクシオンといった非常に軽い質量をもちながら標準理論粒子との相互作用が非常に弱い粒子があげられる。