ABSTRACT

The development of neutrino physics is intimately linked to theoretical studies of the Sun. The Sun is a star going through the Main Sequence phase, the most stable and long evolutionary phase, where stars consume the hydrogen in their cores. Hydrogen burning operates through a series of nuclear reactions that create electron neutrinos νe which escape freely from the solar interior and reach the Earth. Detecting solar neutrinos seemed, in the 1960s, a good astrophysics experiment where to test stellar structure and evolution theories. Ray Davis led the team that built the first chlorine neutrino detector and John Bahcall computed the first Standard Solar Models (SSMs) and estimated the theoretical solar neutrino fluxes. In 1968, when results from the neutrino experiment and the solar model were put together the “solar neutrino problem” was born (a brief account of the situation at that moment can be found in Bahcall 1971). The solar neutrino problem lived for almost 35 years, until 2002, when the Sudbury Neutrino Observatory announced the results of the neutral current experiment (Ahmad et al. 2002). Astrophysics had shown the way to new physics. Solar neutrino predictions from SSM calculations have been extensively used to help constraining neutrino parameters such as mixing angles and mass splitting. The solar neutrino problem is solved, but only the rare 8B solar neutrino flux has been directly measured so far. It remains for neutrino experiments to detect the lower energy neutrinos generated in nuclear reactions more relevant to the solar, and stellar, energetics. We hope to learn stellar astrophysics from these neutrino experiments, going back in this way to the original proposal by Ray Davis and John Bahcall.