What will the first year of SNO show?

The ratio of the measured to the predicted standard model CC event rates in SNO will be 0.47 if no oscillations occur. The best-fit active oscillation predictions for the CC ratio are: 0.35-39 (MSW) and 0.38-42 (vacuum) (all for a 5 MeV energy threshold), typically about 20% less than the no-oscillation expectation. We calculate the predicted ratios for six active and sterile neutrino oscillation solutions allowed at 99% CL and determine the dependence of the ratios on energy threshold. If the high-energy anomaly observed by SuperKamiokande is due to an enhanced hep flux, MSW active solutions predict that out of a total of 5000 CC events above 5 MeV in SNO between 49 and 54 events will be observed above 13 MeV whereas only 19 events are expected for no-oscillations and a nominal standard hep flux.Comment: Phys Lett accepted. Editorial corrections. Related material and viewgraphs at http://www.sns.ias.edu/~jn

How many sigmas is the solar neutrino effect?

The minimal standard electroweak model can be tested by allowing all the solar neutrino fluxes, with undistorted energy spectra, to be free parameters in fitting the measured solar neutrino event rates, subject only to the condition that the total observed luminosity of the sun is produced by nuclear fusion. The rates of the five experiments prior to SNO (chlorine, Kamiokande, SAGE, GALLEX, Super-Kamiokande) cannot be fit by an arbitrary choice of undistorted neutrino fluxes at the level of 2.5 sigma (formally 99% C.L.). Considering just SNO and Super-Kamiokande, the discrepancy is at the 3.3 sigma level(10^{-3} C.L.). If all six experiments are fit simultaneously, the formal discrepancy increases to 4 sigma (7*10^{-5} C.L.). If the relative scaling in temperature of the nuclear reactions that produce 7Be and 8B neutrinos is taken into account, the formal discrepancy is at the 7.4 sigma level.Comment: 1 figure; related information at http://www.sns.ias.edu/~jn

Recent Work on Standard Solar Models

Recent results on standard solar models are reviewed. I shall summarize briefly three of the themes that I stressed at the Neutrino '92 Conference: 1) Different solar model codes give the same answers when the same input data are used; 2) Improved calculations of standard solar models include helium diffusion, the Livermore radiative opacity, the meteoritic iron abundance, and a variety of other corrections; and 3) There are a few basic rules that should be followed in using standard solar models. At the Neutrino '92 Conference, I reviewed in more detail the recent work on standard solar models by Marc Pinsonneault and myself. This work has by now appeared in print (Rev. Mod. Phys. 64, 885, 1992, hereafter Paper I, and ApJ Letters, 69, 717, 1992, Paper II). Therefore, there is no need for me to repeat the details here.Comment: 4 pages, Institute for Advanced Study number AST 92/5

What Do Solar Models Tell Us About Solar Neutrino Experiments?

If the published event rates of the chlorine and Kamiokande solar neutrino experiments are correct, then the energy spectrum of neutrinos produced by the decay of $^8$B in the sun must be different from the energy spectrum determined from laboratory nuclear physics measurements. This change in the energy spectrum requires physics beyond the standard electroweak model. In addition, the GALLEX and SAGE experiments, which currently have large statistical uncertainties, differ from the predictions of the standard solar model by $2 \sigma$ and $3 \sigma$, respectively.Comment: 4 pages (LaTeX file, figures not included

Solar Neutrinos: Where We Are, Where We Are Going

This talk answers a series of questions. Why study solar neutrinos? What does the combined standard model (solar plus electroweak) predict for solar neutrinos? Why are the calculations of neutrino fluxes robust? What are the three solar neutrino problems? What have we learned in the first thirty years of solar neutrino research? For the next decade, what are the most important solvable problems in the physics of solar neutrinos? What are the most important problems in the astrophysics of solar neutrinos?Comment: uuencoded Z-compressed postscript file; 36 pages with figures. To be published in the Astrophysical Journa

Solar Neutrinos: What Next?

I summarize the current state of solar neutrino research and then give my answer to the question: What should we do next?Comment: NNN99 Workshop, viewgraphs and related information at http://www.sns.ias.edu/~jn