Study of Neutrino Processes in Astrophysics

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1. Neutrino Processes in Stellar InteriorsThe neutrino energy loss rate in stellar interiors has been intensively studied for the following neurtino processes : (1) the plasma neutrino process, (2) the pair neutrino process, (3) the photoneutrino process, (4) the neutrino Bremsstrahlung process, and (5) the recombination neutrino process. In the past decade, one of the authors (Naoki Itoh) together with his collaborators has systematically investigated these neutrino processes using the Weinberg-Salam standard theory for the electro-weak interactions. In particular, during the period of receiving the present Grant-in-Aid for Scientific Research, we have accomplished a complete survey of our work in the past decade on the neutrino processes in stellar interiors. We have also estimated the axial vector current contribution in the plasma neutrino process. It has been found that the contribution is almost negligible compared with that from the vector current. Furthermore, accuracy of the Braaten-Segel approximation has been checked in calculating the neutrino energy loss rate.2. Solar Neutrino ProcessesWe have calculated the neutrino-deuteron cross sections for the solar neutrino energies (2 MeV to 20 MeV). The numerical results have been fitted in terms of analytic formulae.