Neutrino magnetic moments and photo-disintegration of deuterium

Neutrinos with non-zero magnetic moments can dissociate deuterium nuclei by a photon exchange, in addition to the weak neutral current process. We calculate the neutrino-magnetic moment induced photo-dissociation cross section of deuterium using the equivalent photon method. This process would contribute extra events to the neutral current reaction which is observed with high precision in the salt-phase of SNO experiment. Using the SNO data and the recent laboratory measurements of the $^7 Be (p, \gamma) ^8 B$ reaction which give a more precise value of the solar $^8 B$ flux we find that the neutrino effective magnetic moment is $\mu_{eff}^2 = (-2.76 \pm 1.46) \times 10^{-16} \mu_B^2$ which can be interpreted as an upper bound $|\mu_{eff}| < 3.71 \times 10^{-9} \mu_B$ (at $95% CL$) on the neutrino magnetic moments.