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Published December 7, 1964 | Published
Journal Article Open

Neutrino Opacity. II. Neutrino-Nucleon Interactions


The contribution of neutrino-nucleon interactions to the neutrino opacity of matter is studied, special attention being paid to possible astrophysical applications such as supernova explosions. The results of recent accelerator experiments with high-energy neutrinos are used to show that nonresonant neutrino-nucleon scattering does not make a significant contribution to the neutrino opacity for astrophysically important conditions. The results of deep-mine cosmic-ray studies are then used to show that, (a) there are no resonances in the ν_μ-nucleon and ν̅ _μ-nucleon systems with masses less than 60 BeV (laboratory neutrino energies <2×10^(+3) BeV), and (b) there are no resonances in the ν_(e)-neucleon and ν̅_(e)-nucleon systems with masses less than 7 BeV (laboratory neutrino energies <30 BeV). Neutrino absorption by bound nucleons is also discussed and a sum rule is proved for neutrino capture that is sufficiently accurate for most astrophysical applications. The effect of the exclusion principle on the capture cross sections is described and some applications to specific nuclei are presented. The accelerator experiments with high-energy neutrinos are then used to show that neutrino radioactivity, i.e., nuclear de-excitation by emission of a neutrino-antineutrino pair, is a substantially less important mechanism for stellar energy loss than was suggested by some previous estimates.

Additional Information

© 1964 The American Physical Society. Received 20 July 1964; published in the issue dated December 1964. Supported in part by the U. S. Office of Naval Research, the National Aeronautics and Space Administration, and the U. S. Atomic Energy Commission. It is a pleasure to thank R. F. Christy and William A. Fowler for valuable discussions concerning neutrino absorption cross sections. We are grateful to S. A. Colgate for stimulating conversations regarding supernova explosions and to F. Reines for informative discussions of deep-mine cosmic-ray studies. W. A. Fowler and F. Hoyle pointed out (California Institute of Technology Seminar, 1963) the possible importance of neutrino-nucleon scattering for supernova explosions. We are grateful to Fowler and Hoyle for bringing this problem to our attention.

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