Solar Neutrino Physics With Borexino*

Solar neutrino research is moving into an era where precision measurements provide a unique probe of the structure and composition of the Sun's core. The proton-proton (pp) chain and the carbon-nitrogen-oxygen (CNO) cycle are two nuclear fusion processes by which stars convert hydrogen into helium, releasing energy and electron-neutrinos. The neutrino fluxes from these two processes can be used to directly determine the carbon and nitrogen abundances in the solar core region and test Standard Solar Models. Borexino is a liquid scintillator detector targeted at measuring solar neutrinos. It is hosted by the underground INFN Laboratori Nazionali del Gran Sasso in L'Aquila, Italy. Thanks to the unprecedented radio-purity of its liquid scintillator, Borexino has measured the solar neutrino fluxes from the entire pp-chain with high precision. Last fall, after years of efforts in stabilizing the detector thermal and background profile, Borexino achieved the first observation of CNO neutrinos. In this talk, I will review the development of low background technology and the analysis methods used in Borexino.