Neutrino Magnetic Moment Upper Bound From Solar Neutrino Observations

Using the data from SuperKamiokande, Kamiokande and Homestake solar neutrino experiments we derive an upper bound on the magnetic moment of the neutrino and find $\mu_{\nu_e}\leq(2.2-2.3)\times 10^{-10}\mu_{B}$, within four different standard solar models. We assume equal magnetic moments for all neutrino flavours. This limit is obtained when neutrinos do not undergo any "disappearence" mechanism other than the magnetic moment conversion due to the solar magnetic field and for a total or nearly total suppression of the intermediate energy neutrinos. In our work we consider an energy dependent suppression of solar neutrinos. We also point out that the limit may be further reduced if the detector threshold energy in $\nu_{e,x}e^{-}$ scattering with solar neutrinos is decreased.