NEUTRINO REACTIONS ON HE-4 AND THE R-PROCESS

Neutrinos from a Kelvin-Helmholtz-cooling neutron star drive the winds in which the r-process of nudeosynthesis possibly occurs. The neutrin os establish the matter expansion rate, the entropy per baryon, and th e neutron richness in the wind material. Some models of the nucleosynt hesis in neutrino-driven winds have successfully reproduced the solar r-process isotopic patterns and yields. An effect not previously inclu ded in these models, however, is the interaction of neutrinos with the abundant He-4 nuclei. Such interactions tend to inhibit the r-process by allowing the assembly of too many seed nuclei, thereby destroying the good agreement between model yields and solar system abundances. I n order to restore that good agreement, it is necessary to postulate s ome modification or modifications to current models.