Limit on the Electron Neutrino Magnetic Moment from the Kuo-Sheng Reactor Neutrino Experiment

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of $1 k{g}^{{{-}}1} ke{V}^{{{-}}1} da{y}^{{{-}}1}$ at 12--60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of ${{μ}}_{{{{ν}}}ₑ}<1.3×{}{10}^{{-}10}{{μ}}B$ at $90%$ confidence level was derived. An indirect bound of the ${{{ν}}}ₑ$ radiative lifetime of ${m}_{{ν}}³{{τ}}_{{ν}}>2.8×{}{10}¹⁸ e{V}³ s$ can be inferred.