RIKEN

Graduate School of Science, The University of Tokyo

Japan Atomic Energy Agency

Summary

An international collaborative research group led by Visiting Principal Investigator Koji Otsuka and Cooperative Researcher Takashi Abe at the Nuclear Spectroscopy Laboratory, RIKEN Nishina Center for Accelerator Science (NACS), Project Researcher Yusuke Tsunoda at the Research Center for Nuclear Study, Graduate School of Science, The University of Tokyo (at the time of the research, currently a researcher at the Research Center for Computational Science, University of Tsukuba), and Project Researcher Minoru Utsuno of Japan Atomic Energy Agency (JAEA) Senior Staff, and their international research group have clarified the quantum structure of carbon-12 ( ^12C) nuclei (6 protons and 6 neutrons) through first-principles calculations using the supercomputers "K computer" and "Fugaku".

This achievement is expected to contribute to the elucidation of the origin of carbon, which is essential for the earth's environment and the birth of life, as well as to provide a new perspective for understanding alpha decay and predict superheavy-element decay.

The helium ( ^4He ) nucleus is a stable nucleus consisting of two protons and two neutrons strongly bound together, and is also called an alpha (α) particle. During stellar evolution, three alpha particles collide and merge simultaneously to form an unstable ^12C nucleus, often called a "foil state. Some of the ^12C nuclei in this foil state transition to stable ^12C nuclei, but the quantum structure of the foil state has been unknown until now.

In this study, the international research group has shown that the density distribution of nucleons (protons and neutrons) in the ^12C nucleus is not uniform and that an alpha particle-like structure called an "alpha cluster" is a component in the intermediate stage. This result was obtained by large-scale first-principles calculations based on quantum chromodynamics ^[7] using the supercomputers "K computer" and "Fugaku" without assuming the existence of α clusters. 12C nuclei.

The study will be published in the online scientific journal Nature Communications on April27 (JST).

Figure: Nucleon density distribution of α-particles and 12C nuclei in the ground state and in the foil state (ab initio calculation)

The research results were made possible by the participation of Koji Otsuka, Emeritus Professor at The University of Tokyo (now Visiting Associate Professor at RIKEN), Yusuke Tsunoda, Project Researcher (at the time of the research), and Noritaka Shimizu, Project Associate Professor (at the time of the research) at the Research Center for Nuclear Study.

For more information, please visit the RIKEN website.