EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN-PPE/92-109 July 24th, 1992 UPDATED REVIEW OF SOLAR MODELS AND SOLAR NEUTRINO EXPERIMENTS

The Conventional Wisdom that there is a Solar Neutrino Problem and that New Physics is required, is examined. The various Solar Evolutionary Models, (or SSM), are described and in particular the four new 1992 papers. While the Evolutionary models are generally robust, there are important assumptions and uncertainties (screening, nuclear reaction rates etc ) which mean that the errors cannot be small. Diffusion in the Sun is expected to be significant but so far there is no calculation which includes all types of diffusion, especially turbulent diffusion. The new and important helioseismological results are shown to be in agreement with some of the SSM calculations. The experimental results are beginning to be not inconsistent with the SSM calculations. Kamiokande is consistent with SSM calculations except for one with rather small errors. The new GALLEX result is in agreement with all SSM calculations within 1.3 to 2 standard deviations. The 1990 SAGE I experiment is shown to find no evidence of solar neutrinos and is inconsistent with all SSM calculations and with GALLEX. However the new 1991 SAGE II experiment finds neutrino rates not inconsistent with SSM calculations. The Chlorine experiment is significantly below SSM calculations and is inconsistent with Kamiokande. In particular the Chlorine claim that there is a variation of the solar neutrino flux with the inverse of the sunspot activity, which shows a correlation of 5 standard deviation significance, is in contradiction with the results of the Kamiokande experiment which finds no variation of the solar neutrino flux with time. The overall conclusion is that there is no compelling evidence for a Solar Neutrino Problem or need for New Physics. However the neutrinos could still have masses and further experiments with higher statistics are essential as they are one of the rare ways of studying this low mass region. Thus the Solar Neutrino Problem is becoming a Neutrino Mass Quest. Based on a presentation at the IAU Colloquium 137 ‘Inside the Stars’, held at Vienna, 13–17 April 1992 and updated at the IV Rencontres de Blois on Particle Astrophysics, 15-20 June 1992.