Press Releases

DATE2024.07.04 #Press Releases

Experiments prove that three neutrons and three protons each are unstable as nuclei.

Disclaimer: machine translated by DeepL which may contain errors.

Tutorial provides important clues to understanding the powerful forces of nature.

Tohoku University
The University of Tokyo
University of Toyama
Osaka University
Hosei University

Summary of presentation

There are four kinds of forces in nature: gravity, electromagnetic force, weak force, and strong force, but the world of atomic nuclei, where the strong force dominates, is full of unknowns. In recent years, research has been conducted to investigate the stability of artificially generated systems in which only neutrons and protons, which are the nucleons that make up the nucleus, are agglomerated. Previous studies have provided experimental results suggesting the metastability of two-neutron and four-neutron systems. However, the stability of systems with three nucleons, which is necessary to advance our understanding of the strong force, has remained unresolved.

A joint research group led by Associate Professor Kenjiro Miki of Graduate School of Science, Tohoku University, with the participation of Associate Professor Nobuaki Imai of the Graduate School of Science, The University of Tokyo, has generated a quantum system consisting of only three neutrons and three protons, and clarified its instability. This achievement is important for clarifying neutron stars, which exist in large numbers in the universe, from a microscopic standpoint, and also for elucidating the evolution of stars and the process of synthesizing elements. The experiment was conducted using the world's thickest tritium-absorbing titanium target developed by this research group at the Hydrogen Isotope Science Center, University of Toyama, and two accelerator facilities, the RI Beam Factory at the RIKEN Nishina Center for Accelerator Science and the Research Center for Nuclear Physics, Osaka University.

The research results were published online in the American Physical Society journal Physical Review Letters on July 4, 2024 (Japan time).

Figure: Schematic of the nuclear reaction observed in this study
3H and 3He indicate tritium and helium-3 nuclei, respectively. (Measurements in the left and right figures were realized at the RIKEN Nishina Center for Accelerator Science RI Beam Factory and the Research Center for Nuclear Physics, Osaka University, respectively.

Professor Nobuaki Imai (Center for Nuclear Study (CNS)) from the School of Science, The university of Tokyo, participated in this research.

For more information, please visit the website of Tohoku University. *in Japanese


Journal name
Physical Review Letters
Title of paper