Technetium-98 nuclear cosmochronometer synthesized by supernova neutrinos

A team of researchers has theoretically predicted that an unstable isotope Technetium-98 (⁹⁸Tc) could be synthesized by neutrinos emitted from supernova explosions.

A large number of neutrinos are emitted from the proto-neutron star formed during an early phase of a core-collapse supernova. When these neutrinos pass through the outer layers, they partially deposit their energy in the outer layers, leading its supernova explosion. In the outer layers, some nuclides such as Tantalum-180 are newly synthesized by the neutrino-nucleus interaction. There are six neutrino species, electron neutrino, muon neutrino, tau neutrino, and their anti-neutrinos.

Previous studies have shown that the neutrino-isotopes are predominantly produced by five neutrino species except the electron anti-neutrino. If there was a neutrino-isotope synthesized predominantly by the electron anti-neutrino, one could estimate the temperature of the six neutrino species, which are important for understanding the supernova explosion mechanism.

At the present study, first, it was found the possibility that ⁹⁸Tc may be synthesized by the neutrino process.

Next, the expected ⁹⁸Tc abundance was calculated using a supernova explosion model with the neutrino-nucleus interactions involved.

As a result, it was found that ⁹⁸Tc neutrino-process nucleosynthesis is the large contribution (~20%) from charged current reactions with electron anti-neutrinos. It was shown that if the initial abundances of ⁹⁸Tc were to be precisely measured, the ⁹⁸Tc nuclear cosmochronometer could be used to evaluate the initial abundance of ⁹⁸Tc and the duration time from the last core-collapse supernova to the formation of the solar system.

The present result is also important for the average temperatures of the six neutrinos and astronomical observation of the electron anti-neutrino.

This work will be published in Physical Review Letters.

Reference

Authors :	Takehito Hayakawa1,2,*, Haemin Ko3, Myung-Ki Cheoun3, Motohiko Kusakabe4, Toshitaka Kajino2,4,5, Mark D. Usang6, Satoshi Chiba6, Ko Nakamura7, Alexey Tolstov8, Ken'ichi Nomoto8, Masa-aki Hashimoto9, Masaomi Ono10, Toshihiko Kawano11, Grant J. Mathews12
Title of original paper :	Short-Lived Radioisotope 98Tc Synthesized by the Supernova Neutrino Process
Journal :	Physical Review Letters
DOI :	10.1103/PhysRevLett.121.102701
Affiliations :	1National Institutes for Quantum and Radiological Science and Technology, Japan 2National Astronomical Observatory of Japan, Japan 3Soongsil University, Korea 4Beihang University, China 5The University of Tokyo, Japan 6Tokyo Institute of Technology, Japan 7Fukuoka University, Japan 8Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Japan 9Department of Physics, Kyushu University 10RIKEN, Japan 11Theoretical Division, Los Alamos National Laboratory, USA 12University of Notre Dame, USA

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