Last Hope for an astrophysical solution to the solar neutrino problem

Abstract

We discuss what appears the last hope for an astrophysical solution to the solar neutrino problem: a correlated variation of the astrophysical factors for the helium burning cross sections ($S_{33}$ and $S_{34}$) and either $S_{17}$ or the central temperature $T_c$. In this context, we recognize the important role played by the CNO neutrinos. In fact, we can obtain a fair fit to the experimental data only if three conditions are met simultaneously: the astrophysical factor $S_{33}$ is about 200 times what is presently estimated, the astrophysical factor $S_{17}$ is about 3 times larger and the ${}^{13}$N and ${}^{15}$O neutrino fluxes are negligible compared to the ones predicted by standard solar models. These conditions are not supported by the present data and their correlated combination is improbable.

11 pages, ReVTeX, plus 3 figures added as uuencoded compressed postscript files. The postscript file with the text and 3 figures is available at ftp://risc0.ca.infn.it/pub/private/lissia/infnca-th9511.ps