Solar Neutrinos and The Standard Solar Model

Abstract

The standard solar model (SSM) yield a $^8$B solar neutrino flux which is consistent within the theoretical and experimental uncertainties with that observed at Super-Kamiokande. The combined results from the Super- Kamiokande and the Chlorine solar neutrino experiments do not provide a solid evidence for neutrino properties beyond the minimal standard electroweak model. The results from the Gallium experiments and independently the combined results from Super-Kamiokande and the Chlorine experiment imply that the $^7$Be solar neutrino flux is strongly suppressed compared with that predicted by the SSM. This conclusion, however, is valid only if the neutrino absorption cross sections near threshold in Gallium and Chlorine do not differ significantly from their theoretical estimates. Such a departure has not been ruled out by the Chromium source experiments in Gallium. Even if the $^7$Be solar neutrino flux is suppressed compared with that predicted by the SSM, still it can be due to astrophysical effects not included in the simplistic SSM. Such effects include spatial and/or temporal variations in the temperature in the solar core induced by the convective layer through g-modes or by rotational mixing in the solar core, and dense plasma effects which may strongly enhance p-capture by $^7$Be relative to e-capture. The new generation of solar observations, which already look non stop deep into the sun, like Super-Kamiokande through neutrinos, and SOHO and GONG through acoustic waves, may be able to point at the correct solution; astrophysical solutions if they detect unexpected temporal and/or spatial behaviour, or particle physics solutions if Super-Kamiokande detects characteristic spectral distortion or temporal variations (e.g., the day-night effect) of the $^8$B solar neutrino flux . If