Neutrino properties studied with a triton source and a large spherical TPC

The purpose of the present paper is to study the neutrino properties as they may appear in the low-energy neutrinos emitted in triton decay: (13H→23He+e-+νbare) with maximum neutrino energy of 18.6 keV. The technical challenges to this end can be summarized as building a very large Time Projection Counters (TPC) capable of detecting low-energy recoils, down to 100 eV, within the required low background constraints. More specifically we propose the development of a spherical gaseous TPC of about 10-m in radius and a 200 Mcurie triton source in the center of curvature. One can list a number of exciting studies, concerning fundamental physics issues, that could be made using a large-volume TPC and low-energy antineutrinos: (1) The oscillation length involving the small angle δ=sin θ13, directly measured in our νe disappearance experiment, is fully contained inside the detector. Measuring the counting rate of neutrino-electron elastic scattering as function of the distance of the source will give a precise and unambiguous measurement of the oscillation parameters free of systematic errors. In fact first estimations show that even with a year's of data taking a sensitivity of a few percent for the measurement of the above angle will be achieved. (2) The low-energy detection threshold offers a unique sensitivity for the neutrino magnetic moment which is about two orders of magnitude beyond the current experimental limit of 10-10μB. (3) Scattering at such low neutrino energies has never been studied and any departure from the expected behavior may be an indication of new physics beyond the standard model. We present a summary of various theoretical studies and possible measurements, including a precise measurement of the Weinberg angle at very low momentum transfer