Borexino and solar neutrinos

Abstract

The neutrino oscillation is one of the most important insights of the last decades in the physics of the elementary particles. The study of the solar neutrinos has been of fundamental importance in understanding the neutrino experimental behavior. The Standard Solar Model is the unavoidable basis and the MSW effect the most important hypothesis for this study. After the pioneering radiochemical data and the Cherenkov experiments, which have given the first proof of the oscillation in the solar-neutrino sector, Borexino succeeded to extend the study to almost the entire spectrum of the solar neutrinos, being a unique experiment able to detect in real time the neutrino interactions down to ~ 200 keV, thanks to its unprecedented radio-purity. In this way the analysis of the oscillations has been extended to the vacuum regime, while the shape of the transition region vacuum-matter has to be refined after the first Borexino results. This study is carried on exploiting the upgraded performances of the detector, while other experiments in construction or in design phase will adress the same problem.