On solar model solutions to the solar neutrino problem.

Abstract

Without assuming any solar neutrino spectra but merely assuming pure ${\ensuremath{\nu}}_{\mathit{e}}$ emissions from the Sun, neutrinos seen by the Kamiokande experiment should produce at least 2.6\ifmmode\pm\else\textpm\fi{}0.45 SNU in the lower threshold Homestake experiment. This rate is compared with the total event rate of 2.55\ifmmode\pm\else\textpm\fi{}0.25 SNU observed by the Homestake experiment which solar models tell us should measure not only $^{8}\mathrm{B}$ neutrinos seen by the Kamiokande but also uncertainty-free pep neutrinos (which contribute 0.2 SNU) as well as $^{7}\mathrm{Be}$ neutrinos whose energies are below the Kamiokande threshold. This comparison may imply that $^{7}\mathrm{Be}$ neutrinos are more severely suppressed than the $^{8}\mathrm{B}$ neutrinos with respect to the predictions of standard solar models, which cannot be explained by any known astrophysics solution. (In particular, this argument is independent of uncertainties in solar nuclear reaction rates.) It is also noted that the lower limit that the Kamiokande observations set on the $^{8}\mathrm{B}$ neutrino flux restricts variations of standard solar models to require minimal rates of 3.6 SNU for the Homestake experiment and 114 SNU for GALLEX and SAGE to achieve consistency (and still fit helioseismic data). Therefore, variations of standard solar models as solutions to the solar neutrino problem are inconsistent with the Homestake experiment and only marginally allowed by the gallium experiments. If the gallium experiments eventually confirm a flux significantly below 114 SNU, it would seem to imply new neutrino physics.