Evidence of a Secondary Bow in a Nuclear Rainbow

Research Press Release | June 23, 2014

Press Release
Key Points Evidence of the existence of a secondary bow in a nuclear rainbow, previously believed to be non-existent in principle, has been discovered.

・From the discovery of the secondary bow, long-standing mysteries regarding interactions which act between nuclei have been solved.

Overview Similar to those seen on Earth, rainbows can be observed in the microscopic world of nuclei. These are caused solely by refraction (zero reflection) as incident particles are strongly bent by strong nuclear forces, which was theoretically founded by Professor Hideki Yukawa, Japan’s first Nobel laureate. This type of rainbow (Newton’s zero-order nuclear rainbow) cannot occur on Earth. Since reflection is not involved, secondary bows, as observed in meteorological rainbows, had been believed to be non-existent in principle. However, we theoretically showed the existence of secondary bows caused solely by refraction. A stripe-patterned bright region can be faintly observed on the dark side of a nuclear rainbow when the oxygen nucleus was bombarded on the carbon nucleus at the high energy of around 300 MeV. We could identify a secondary bow in this region, which had been puzzling for long time by analyzing the experimental data. This is the first discovery since the days of Aristotle in the pre-Christian Era of a secondary bow caused solely by refraction in more than 2,000 years of rainbow research.

Yoshiharu Hirabayashi, Assoc. Professor, Information Initiative Center (Jpn page), Hokkaido University

TEL: +81-11-706-3545


Shigeo Okubo, Research Fellow, Research Center for Nuclear Physics





Publications  Physical Review C (2014.5.8)