Research report 2003 - Max Planck Institute for Nuclear Physics

Solving the Solar Neutrino Problem: The Achievement of the GALLEX-GNO Experiment

Authors
Hampel, Wolfgang
Departments

Astroteilchenphysik (Prof. Dr. Heinrich Völk)
MPI für Kernphysik, Heidelberg

Summary
The detection of neutrinos produced in the nuclear fusion reactions in the interior of the sun allows to experimentally test the theory of energy generation in the sun. The first experiments of this kind could essentially only measure 8B neutrinos created in a rare side branch of hydrogen fusion which is totally negligible for energy production in the sun. The results showed a deficit of a factor 2-3 when compared to the expectation from the Standard Solar Model, a fact which has been called the "solar neutrino problem". This raised the question: Are the main branches responsible for energy generation in the sun and the corresponding neutrinos (pp and 7Be) also affected by these problems? Providing the answer to this question has been the main motivation for performing the GALLEX-GNO experiment. The result obtained in more than ten years of operation revealed again a deficit of about 45% when compared to the Standard Solar Model prediction. Since there are no reasonable astrophysical explanations for this finding, there remains only the particle physics solution, according to which neutrinos have a non-zero rest mass and undergo oscillations. This conclusion has recently be definitively confirmed by the results of the SNO solar neutrino detector in Canada.

For the full text, see the German version.

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