New limits on heavy sterile neutrino mixing in 8B decay obtained with the Borexino detector
G. Bellini et al. (Borexino Collaboration)
Phys. Rev. D 88, 072010 – Published 29 October 2013
[doi:10.1103/PhysRevD.88.072010] (preprint on arXiv)
If heavy neutrinos with mass mνH≥2me are produced in the Sun via the decay 8B→8Be+e++νH in a side branch of the pp chain, they would undergo the observable decay into an electron, a positron and a light neutrino νH→νL+e++e−. In the present work Borexino data are used to set a bound on the existence of such decays. We constrain the mixing of a heavy neutrino with mass 1.5 MeV≤mνH≤14 MeV to be |UeH|2≤(10−3−4×10−6), respectively. These are tighter limits on the mixing parameters than obtained in previous experiments at nuclear reactors and accelerators.