A New Hypothesis to Explain the Source of Nucleon Spins: Japan Takes on a Key Role in an International Collaborative Study

Natural science explores and tries to understand various objects and events in the natural world. Of these, Professor Iwata continues to pursue the internal structures of protons and neutrons, which are one of the smallest units of matter. He is participating in the COMPASS Collaboration—an international joint research project with over 200 researchers from 13 nations—as the leader of Japanese participants and has been conducting research work at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland, for many years. A nucleon (collective term referring to protons and neutrons) is formed by elementary particles called quarks bonding with each other. It can rotate by itself like a spinning top and this property is known as “spins.” Nucleon spins were once thought to be caused by quark spins, but previous studies have revealed that the effect of quark spins is only about 30%. This has been a great source of headache to physicists around the world, to the extent that some call it the “spin crisis.” The answer to what the true source of nucleon spins is, is being longed for.
In the study to find the source of nucleon spins using the polarized target at CERN—the largest in the world—the group of Japanese researchers led by Professor Iwata is playing a central role through the use of spin polarized target and large hydrogen target technologies. The COMPASS Collaboration currently focuses not on the rotation of quarks inside nucleons but on their orbital motion (revolution).

Backing for the Mystery Solving and the Globalization of Our University: Nucleon Spin Study Wins Grants-in-Aid for Scientific Research

Although existing theories state that quark orbital motions have no effect on nucleon spins, results from studies by Professor Iwata et al., suggest that they do affect nucleon spins. To confirm that effects of quark orbital motions exist, data needs to be strengthened by taking even more precise measurements. The study on nucleon spins to do this, under the research title “Study of Nucleon Spin Structure in Quark Level with a Large Polarized Target” was accepted by the Grants-in-Aid for Scientific Research (S) program. Grants-in-Aid for Scientific Research programs cover all research fields from humanities, social science to natural science. They aim to support all kinds of basic to applied research projects that are creative and/or pioneering. The basic studies program “(S)” provides the second largest grants and this is the first time that Yamagata University was selected. We can see that expectations are high for revealing the source of nucleon spins and establishing a novel elementary particle theory.
The research project is expected to be funded for four years, starting in FY 2020. It is anticipated that the funding facilitates the international joint study at CERN in Geneva, Switzerland, and that its effects would extend to further globalization at our university. The project roadmap shows that experiments will be conducted on a 24-hour basis for approximately six months, both in 2021 and 2022, and data analysis will take place in parallel to write an academic paper, leading to publication of the findings in 2023.

Research Conducted Remotely Due to the COVID-19 Pandemic: Prioritizing Research Outcomes and Student Capacity Building at the Same Time

The Japanese group of researchers for COMPASS consists of members from Yamagata University, University of Miyazaki, Chubu University and the High Energy Accelerator Research Organization (KEK). Currently, Dr. Norihiro Doshita, an assistant professor at Yamagata University who was trained under Professor Iwata, is stationed in Geneva. Dr. Doshita is in charge of making adjustments to the COMPASS large polarized target. Professor Iwata was also hoping to come and go between Yamagata University and CERN but he is being unable to do so because of the COVID-19 pandemic. Yet still, there seems to be no negative effects on the research plan: he says that he can check the polarized target apparatus at CERN from Yamagata University on a screen and even make adjustments like turning valves.
Professor Iwata has been participating in the international collaborative study at CERN since 1991. His motivation comes from his inquisitive mind, eager to solve mysteries in the natural world. “While research work that can help people is necessary, it is also important to probe into scientific principles. New discoveries tend to be born from failure, more often than we think. Eccentric ideas from students can provide clues too,” he says. Professor Iwata would like to take many students to Geneva, a hub of many international organizations, and allow them to nurture wider global perspectives. The university would like to closely watch the ongoing COMPASS Collaboration while anticipating that it will bring successful outcomes and nurture young researchers who can take up new quests along the way.