We investigate the nucleosynthesis process in high-entropy () and very fast?expanding () materials. In such a material with the electron fraction near 0.5, an interesting nucleosynthesis process occurs. In this process, the abundance distribution of heavy?nuclei of achieves quasi-statistical equilibrium (QSE) at high temperature and the abundances are frozen at the end of the nucleosynthesis. We explain this abundance distribution using the "alpha-constrained QSE" abundances formulated in this paper. We demonstrate that this nucleosynthesis would occur in neutrino-driven winds from massive proto-neutron stars in hypernovae, where ?p-nuclei are synthesized.
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