Probing non-standard couplings of neutrinos at the Borexino detector

Abstract

The present experimental status does not exclude weak-strength non-standard interactions of neutrinos with electrons. These interactions can be revealed in solar neutrino experiments. Our discussion covers several aspects related to this issue. First, we perform an analysis of the Super-Kamiokande and SNO data to investigate their sensitivity to such interactions. In particular, we show that the ν e oscillation into sterile neutrinos can be still allowed if ν e has extra interactions of the proper strength. Second, we suggest that the Borexino detector can provide good signatures for these non-standard interactions. Indeed, in Borexino the shape of the recoil electron spectrum from the νe→ νe scattering essentially does not depend on the solar neutrino conversion details, since most of the signal comes from the mono-energetic 7Be neutrinos. Hence, the partial conversion of solar ν e into a nearly equal mixture of ν μ and ν τ , as is indicated by the atmospheric neutrino data, offers the chance to test extra interactions of ν τ , or of ν e itself.