Upper limit on the neutrino magnetic moment from three years of data from the GEMMA spectrometer

Abstract: The result of the 3-year neutrino magnetic moment measurement at the Kalinin Nuclear Power Plant with the GEMMA spectrometer is presented. Antineutrino-electron scattering is investigated. A HPGe detector of 1.5 kg placed at a distance of 13.9 m from the centre of the 3 GW_th reactor core is used in the spectrometer. The antineutrino flux is 2.7x10^13 1/cm^2/s. The differential method is used to extract nu-e electromagnetic scattering events. The scattered electron spectra taken in 5184+6798 and 1853+1021 hours during the reactor ON and OFF periods respectively are compared. The upper limits for the neutrino magnetic moment with and without atomic ionization mechanism were found to be 5.0x10^-12 and 3.2x10^-11 Bohr magnetons at 90% CL, respectively.