Sin2 θW estimate and neutrino electromagnetic properties from low-energy solar data

Abstract

We report new values of weak-mixing angle (), neutrino effective magnetic moment () and the charge radii using the lowest energy (to-date) solar neutrino data of pp, 7Be and pep spectra from phase I and phase II runs of Borexino experiment. The best-fit values obtained are at 1σ with a precision comparable to that of the combined reactor and accelerator very short-baseline experiments and at 90% C.L. with a factor of 3 improvement over the previous bounds. This leads to the improvement of constraints on all the related magnetic moment matrix elements for the Majorana-type and Dirac-type neutrinos in mass basis and also stronger bounds on the magnetic moment flavor states. The bounds on the neutrino charge radii obtained are cm2 cm2 and cm2 cm2 at 90% C.L.