Precise formulation of perturbative QCD and high precision determination of fundamental physical constants

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05404
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Tohoku University
• Principal Investigator: Sumino Yukinari 東北大学, 理学研究科, 准教授 (80260412)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 摂動ＱＣＤ / リノーマロン / ループ計算 / 物理定数 / 演算子積展開 / 非摂動効果

Outline of Final Research Achievements

Out of four forces of Nature "Gravitational, Electromagnetic, Strong and Weak Forces," the strong force is the source of gigantic energy in the Sun and a potential candidate of our future energy resource. As yet it is not under human's control. Main reason is the lack of our ability to accurately predict the nature of the force and reveal its detailed features. Nonetheless, during more than 40 years since the discovery of QCD, the fundamental theory of the strong force, our understanding and predictability have advanced considerably. Determination of the fundamental parameter of QCD, alpha_s, has played the role of milestone in this progress: To improve its accuracy many difficulties were needed to be overcome, while once it is determined more precisely, it serves as the input parameter in the predictions of all the QCD phenomena. In the current research we have solved a previously unsolved problem, known as the renormalon problem, and achieved a precise determination of alpha_s.

Free Research Field

摂動ＱＣＤ

Academic Significance and Societal Importance of the Research Achievements

強い力の現象を予言するための有力な方法として物理量をαsの摂動展開で計算する「摂動ＱＣＤ」が発展してきた。高度な計算技術が発達し、例えば近年のＬＨＣ実験におけるヒッグス粒子の発見に貢献した。摂動ＱＣＤで予言精度向上の障壁となるのがリノーマロン問題である。強い力が低エネルギーでより強くなることを反映して、低エネルギーで摂動展開の収束性が悪くなる。この問題を解決するために演算子積展開(OPE)と組み合わせて予言を行なった。鍵となったのは、OPE中の非摂動効果に吸収できる形で摂動級数からリノーマロンを分離する方法の開発であった。クォーク間力の摂動計算でこれを実現して、高精度でαsを決定した。