A collaborative research group led by Taketo Hayakawa, Senior Researcher of the Quantum Science and Technology Research and Development Organization, predicted by theoretical calculation that neutrinos emitted by supernova explosions would produce technetium-98 (98Tc), which does not exist in nature.Researchers from the National Astronomical Observatory of Japan, the University of Tokyo, Tokyo Institute of Technology, Kyushu University, Institute of Physical and Chemical Research, etc. participate in the research group.
A star with a mass more than eight times that of the Sun will undergo a gravitational collapse supernova explosion at the end of its life.In the early stages of this explosion, a huge number of neutrinos (elementary particles) are emitted from the central primordial neutron star, and the neutrinos drop part of their energy to the outer layer, causing a supernova explosion.At this time, some neutrinos react with existing nuclei to produce new nuclides such as tantalum 8. Of the 180 types of neutrinos (Note), 6 types of neutrinos other than anti-electron neutrinos were known to produce the above nuclides.If there is a nuclide with a large contribution of anti-electron neutrinos, the average energy of all 5 types of neutrinos can be evaluated, which greatly contributes to the understanding of supernova explosions.
The research group realized that 98Tc might have been produced in neutrinos, calculated the associated neutrino nuclear reaction rate, and calculated the amount of 98Tc produced using a supernova explosion model.As a result, it was found that the contribution of anti-electron neutrinos was up to 20%, which was the first discovery of a heavy element with a large contribution of anti-electron neutrinos.He also showed that if meteorite research progresses, the amount of 98 Tc during the formation of the solar system and the age of the supernova explosion can be evaluated.
This research is said to contribute to the elucidation of the average energy of all six types of neutrinos in supernova explosions and the prediction of the energy of anti-electron neutrinos in supernova explosions expected in the near future.
(Note) Six types of electron neutrinos, μ neutrinos, τ neutrinos and their antineutrinos, anti-electron neutrinos, anti-μ neutrinos, and anti-τ neutrinos.
Paper information:[Physical Review Letters] Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process
