Determination of the size of the repulsive core due to the quark Pauli effect in the Sigma-Nucleon interaction by a Sigma-proton scattering

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H05442
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Tohoku University
• Principal Investigator: Miwa Koji 東北大学, 理学研究科, 准教授 (50443982)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: ストレンジネス核物理 / ハイペロン陽子散乱実験

Outline of Final Research Achievements

We have performed a Sigma proton scattering experiment at the J-PARC hadron experimental facility and could establish the experimental method for a high statistics Sigma proton scattering experiment. Because the lifetime of Sigma hyperon is very short and it decays just after a few cm flight, the scattering experiment between Sigma hyperon and proton was quite difficult. In order to overcome the experimental difficulty, we proposed a new experimental method where a high intensity pi beam was used to produce a lot of Sigma hyperons. A recoiled proton detector which is dedicated to this experiment was developed. In our experiment, we could identify about 150 Sigma proton scattering events from the analysis of two-days beam time. We expect about a several thousand of scattering event can be identified during the whole experimental data which is about 100 times more statistics. We will soon derive a differential cross section.

Free Research Field

原子核物理学

Academic Significance and Societal Importance of the Research Achievements

現在まで、シグマ粒子のようなストレンジクォークを持つハイペロンと陽子の相互作用の究明は、ハイペロンを原子核に入れたハイパー核の研究から行われていた。これは散乱実験が困難であったことが大きな要因である。本研究においてΣと陽子の散乱実験の手法を確立し、ΣNの2体の相互作用を散乱実験から決定する道筋を作ることが出来た。今後はΣ粒子の他にΛ粒子と陽子の散乱実験なども検討し、２体の相互作用は散乱実験で決定し、原子核の持つ多体効果をハイパー核構造から調べるという新たな流れを確立できると考える。これは宇宙に浮かんでいる巨大な原子核とも言える中性子星の内部構造を解明することにも繋がると考えている。