Search for neutrino radiative decay with a prototype Borexino detector

Abstract

Results of background measurements with a prototype of the Borexino detector were used to obtain bounds on the lifetime of radiative neutrino decay νH→νL+γ. The new lower limit for the lifetime of pp and 7Be neutrinos is τc.m.(νH→νL+γ) /mν≥4.2×103 s eV−1(α)= 0). It is more than an order of magnitude stronger than the value obtained in previous experiments using nuclear reactors and accelerators.