Probing the nature of the neutrino: The boron solar-neutrino experiment

With a welter of neutrino scenarios and uncertain solar models to be unraveled, can solar-neutrino experiments really break new ground in neutrino physics? A new solar-neutrino detector BOREX, based on the nuclide ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, promises the tools for a definitive exploration of the nature of the neutrino and the structure of the Sun. Using double-mode detection by neutrino excitation of ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ via the neutral-weak-current- and the charged-current-mediated inverse β decay in the same target, independent measurements of the total neutrino flux regardless of flavor and the survival of electron neutrinos in solar matter and a vacuum can be made. Standard models of the Sun, and almost every proposed nonstandard model of the neutrino, can be subjected to sharp and direct tests. The development of BOREX, based on B-loaded liquid-scintillation techniques, is currently in progress.