Nucleosynthesis of Radioactive Nuclei in Explosive Stellar Objects and Cosmic and Galactic Ages

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We tried model construction on of n tern with high precision, summing the progress in theoretical studies of explosive nucleosynthesis, observational anal astronomy, and nuclear experiment in this project Comparing our theoretical model calculations with observed elemental abundances of long-lived radioactive nuclei in metal-deficient halo stars, we found that the U-Th chronometer has better precision than the UT-Eu chronometer. Long-lived radioactive nuclei are produced d either in rapid-neutron capture process (r-process) in supernova explosion and in slow-neutron capture process (s-process) in War stage of small-to-intermediate mass AGB stars. Physical conditions of astrophysical nucleosynthesis environments were dared theoretically in numerical simulation of explosive nude synthesis It was found that neutron and alpha induced reactions on light mass neutron-rich unstable nuclei and neutron capture reactions on intermediate-to-heavy mass neutron-rich unstable nuckei play the importa … More nt roles in the r-process. These cross section data were taken from nuclear experiments which were carried outin experimental facilities of nuclear and particle physics in the world including RIKEN and CNS, University of Tokyo. Unmeasured nuclear data and cuss sections for neutrino-nucleus interactions, which are very important for gravitational collapse of supernovae, were theoretically calculated by the use of the quantum theory for particles and nuclei. Using these experimental and theoretical inputs hum particle and nuclear physics we can carry out nucleosynthesis calculations with better precision and provide reliable initial abundance distribution of the r-process elements. We then applied these products to Galactic chemical evolution in order to theoretically predict time variation of elemental abundances at long-lived radioactive heavy elements such as Th and U. Combining the theoretical prediction with observed data which were taken by using High Dispersion Spectrograph equipped with SUBARU Telescope, we tried to estimate the age of the early generation, metal-deficient halo stars in our constructed cosmochrometers of the r-process elements. We compared the results with the constraints on the cosmic age which was determined from observational cosmology which include several cosmological parameters, and dish consistency between both ages We also studied big-hang nucleosynthesis, cosmic microwave background anisotropy, and luminosity-redshift relation of type Ia supernovae in order to construct cosmological model that is consistent with the cosmic and Galacticages determined in our project Less