Exploring Supersymmetric Standard Models as a Solution to the Fine-tuning Problem of the Electroweak Scale

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K14270
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: The University of Tokyo
• Principal Investigator: Nagata Natsumi 東京大学, 大学院理学系研究科(理学部), 助教 (60794328)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 超対称性理論 / 大統一理論

Outline of Final Research Achievements

The electroweak symmetry in the Standard Model is broken by the vacuum expectation value of the Higgs field at the electroweak scale. Since this value is highly sensitive to quantum corrections, it has widely been believed that huge amount of fine-tuning among parameters in the theory is required to keep it around the electroweak scale. In this study, I constructed a supersymmetric Standard Model that solves this electroweak-scale fine-tuning problem based on the so-called relaxion mechanism. In addition, I showed the testability of such models with the search of long-lived particles in the future LHC experiments. I also discussed ultraviolet completion of these models in the framework of supersymmetric Grand Unified Theories, and showed that future proton-decay experiments are able to distinguish these Grand Unified Models.

Free Research Field

素粒子論

Academic Significance and Societal Importance of the Research Achievements

電弱スケール微調整問題は，長年にわたって素粒子標準模型における理論的課題であり，またLHCにおいて新粒子が発見されると期待される理由となっていた。しかしながら，LHCにおいて標準模型を超える物理が発見されていない現状を踏まえた今，電弱スケール微調整問題を説明する新たなパラダイムが求められていた。そのような可能性を実際に提示した点，また将来実験における検証可能性を明らかにした点で，本研究は意義深いといえる。