This conceptual art illustrates the different sizes of proton (charge) and neutron distributions in calcium-48, calculated by nuclear physicists with the help of fastest supercomputers available for public research.Photo courtesy of the MSU National Superconducting Cyclotron LaboratoryA team of researchers, led by Gaute Hagen of the Oak Ridge National Laboratory that includes two Michigan State University nuclear physicists – Morten Hjorth-Jensen and Witold Nazarewicz – has uncovered some of the mysteries of the nucleus of the atom.

The findings are detailed in this week’s edition of the scientific journal Nature Physics.

More precisely, the team was able to answer a basic question: What is the size of the atomic nucleus?

The researchers solved this puzzle by using Titan, the country’s most powerful supercomputer housed at the Oak Ridge National Laboratory.

Atomic nuclei are collections of protons and neutrons and reside at the core of all matter, as well as serve as the fuel that keeps stars burning for billions of years.

Using Titan, the team computed the neutron distribution and other information on calcium-48, an isotope with an atomic nucleus consisting of 20 protons and 28 neutrons. This revealed that the difference between the radii of neutron and proton distributions – called the “neutron skin” – is considerably smaller than previously thought.

“No one has ever succeeded in solving the nuclear 48-body problem using the realistic nuclear forces,” said Nazarewicz, chief scientist for the Facility for Rare Isotope Beams and an MSU Hannah Distinguished Professor. “So this in itself is a breakthrough.”

Witold Nazarewicz is the chief scientist at the Facility for Rare Isotope Beams and an MSU Hannah Distinguished Professor in physics. He is part of an international team of researchers that is unlocking the mysteries of atomic nuclei.Photo courtesy of the Facility for Rare Isotope BeamsAdvancing our knowledge of the atomic nucleus is a “big deal” said Nazarewicz, as it is at the core of all visible matter in the universe and composes 99.9 percent of its mass.

He said this and future research will help us control, both in the laboratory and with computers, this basic building block of matter. The now under-construction Facility for Rare Isotope Beams at MSU will be a world leader in this area of research.

Once completed, FRIB will be a world-leading laboratory for the study of nuclear structure, reactions and astrophysics. Experiments with intense beams of rare isotopes produced at FRIB will help provide a comprehensive description of nuclei, shed new light on the origin of the elements, help provide an understanding of matter in neutron stars and establish the scientific foundation for innovative applications of nuclear science to society.

Other members of the research team included scientists from the University of Tennessee, Chalmers University of Technology (Sweden), TRIUMF (Canada), Hebrew University (Israel), Technical University Darmstadt (Germany), the University of Oslo (Norway) and the University of Trento (Italy).

This research was supported by the U.S. Department of Energy Office of Science, in part through an Office of Science Early Career Research Program Award to Hagen. In addition, the work used resources of the Jülich Supercomputing Center in Germany. Other support came from the U.S. National Science Foundation, the European Research Council, the United States–Israel Binational Science Foundation, and the governments of Canada, Italy, Norway and Sweden.