The main reason that our paper is highly cited is that the SNO collaboration provided fundamental new data that made possible some remarkable inferences, including the results that the observed total 8B neutrino flux from the Sun is in excellent agreement with the predicted standard solar model neutrino flux and that the neutrino flavor oscillations are unambiguously observed for solar neutrinos. The fact that the SNO collaboration generously made their data available in a convenient form, with full explanations of how to use those data, permitted us and other theoretical groups to quickly and effectively utilize the data for a variety of different applications. The collaborations for other important solar neutrino experiments performed earlier have similarly made their data available in convenient form. These include the Kamiokande and Super-Kamiokande experiments in Japan, the SAGE data from Russia, the GALLEX obtained in the Gran Sasso underground laboratory in Italy , and the original chlorine data obtained in the Homestake Gold Mine in South Dakota, US. Progress in the field of solar neutrino research is obtained through a community activity, with mutually supportive interactions between different experimental groups and between theorists and experimentalists. I should also mention that writing this paper was a wonderful experience for me since I got to work with Carlos Pena-Garay and his thesis advisor, Concha Gonzalez-Garcia. They are both outstanding scientists, who work very hard (and as far as I can tell, never sleep), and really fun people. I learned an enormous amount by collaborating with them.

  Does it describe a new discovery or a new methodology that's useful to others? 

Yes, we introduced several technical improvements in the analysis procedures for studying solar neutrino oscillations. In addition, I think our results were of special interest because we provided detailed predictions with uncertainties for 10 observables that can be measured in future solar neutrino experiments. These predictions are based upon our analyses of all of the existing solar and reactor data.

  Could you summarize the significance of your paper in layman's terms? 

Our paper made use of recently published data from the Sudbury Neutron Observatory in Sudbury, Ontario and from other observatories located deep underground around the world in order to study neutrinos from the Sun. Neutrinos are exotic particles produced in nuclear processes that are uncharged, almost massless, that travel close to the speed of light, and interact very little with matter. They can be used to look inside the Sun and to observe the nuclear reactions that take place in the very center of the Sun. The nuclear reactions supply the sunshine that is responsible for all life on Earth. The new data led to two especially important conclusions. One, neutrinos change their type on the way to the Earth from the interior of the Sun. This result means that the standard model of particle physics must be modified to include the possibility of neutrinos changing their types. Second, the total flux of neutrinos observed from the Sun is in excellent agreement with theoretical calculations of the predicted flux based upon a detailed model of how the temperature, density, and chemical composition of the interior of the Sun interact. The agreement between the predicted and the observed flux means that astrophysicists understand well how the Sun shines.

  How did you become involved in this research?

I began this research in 1961, when Raymond Davis Jr. asked me if I could calculate the rate at which neutrinos from 7Be would be produced at typical solar temperatures. I did this calculation and only afterwards realized that I needed a detailed model of the Sun in order to really answer the question. I got deeper and deeper into the problem, and more than 40 years later I am still fascinated by questions concerning neutrinos and stars. Right now, I am working hard trying to answer the question of what can be learned from future experiments.

John N. Bahcall
Institute for Advanced Study
School of Natural Sciences
Princeton, NJ, USA

Prof. Concha Gonzalez-Garcia
CN Yang Institute for Theoretical Physics
State University of New York at Stony Brook
Stony Brook, NY, USA