New Phase on Time Reversal Symmetry: The third generation MTV experiment

2021 Fiscal Year Final Research Report

• Project/Area Number: 16H03985
• 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: Rikkyo University
• Principal Investigator: Murata Jiro 立教大学, 理学部, 教授 (50360649)
• Project Period (FY): 2016-04-01 – 2021-03-31
• Keywords: 時間反転対称性 / 物質と反物質 / ベータ崩壊

Outline of Final Research Achievements

An experiment to search for time-reversal symmetry violation was performed and data was successfully collected. The experiment measured the transverse polarization of electron emitted from spin-polarized Li-8 nuclei. The spin-polarized unstable nuclei were produced using ISAC at the TRIUMF in Canada, and a transverse polarimeter based on the principle of measuring the scattering asymmetry of Mott scattering using a cylindrical drift chamber as an electron tracking detector was constructed and used. Experiments were performed in 2016 and 2017 and data were successfully collected, yielding data on R correlations that break time-reversal symmetry, N correlations that do not break time-reversal symmetry but have not been observed before, and time variations of polarized nuclear half-lives that can verify Lorentz symmetry breaking.

Free Research Field

素粒子・原子核物理学、重力物理学

Academic Significance and Societal Importance of the Research Achievements

時間反転対称性は物理法則が持つと信じられている最も基本的な対称性の一つである。これは物質と反物質の対称性の破れとも直接的に関係しており、我々の宇宙に極端に反物質が少ない謎に対する答えを提供する可能性があるものである。この研究はわが国で開発した検出器をカナダに移設し、カナダの加速器を用いて世界最高精度に達するデータを得る事に成功した国際プロジェクトである。