New experimental limits on heavy neutrino mixing in 8B decay obtained with the Prototype of the Borexino Detector

New experimental limits on heavy neutrino mixing in ⁸B-decay obtained with the Borexino Counting Test Facility

Journal of Experimental and Theoretical Physics Letters  Volume 78, pages 261–266 (2003)
Published: September 2003
doi:10.1134/1.1625721  (local copy)

Abstract

If heavy neutrinos with mass are emitted in the decays of ⁸B in the Sun, then ν_H→ν_L+e⁺+e⁻ decays should be observed. In the present work, the results of background measurements with the Borexino Counting Test Facility have been used to obtain bounds on the number of these decays.  As a result, new limits on the coupling |U_eH|² of a massive neutrino in the range of 1.1 MeV to 12 MeV have been derived (|U_eH|²≤10⁻³−10⁻⁵).  The obtained limits on the mixing parameter are stronger than obtained in previous experiments using nuclear reactors and accelerators.