Study of neutrino electromagnetic properties with the prototype of the Borexino detector

Abstract The results of background measurements with the prototype of the Borexino detector (CTF) have been used to obtain an upper bound on the neutrino magnetic moment, μ ν . The new upper limit for μ ν from pp and 7 Be solar neutrinos is (5.5×10 −10 ) μ B (90% c.l.) in the Standard Solar Model scenario. This is the first limit on μ ν obtained using sub-MeV neutrinos. The sensitivity of the prototype to the neutrino charge radius and the neutrino radiative decay are also presented.