New Limits on Neutrino Magnetic Moments from the Kuo-Sheng Reactor Neutrino Experiment

A laboratory has been set up at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core to study low energy neutrino physics. A detector threshold of 5 keV and a background level of 1 counts/day-keV-kg at 12-60 keV was achieved with a high purity germanium detector of mass 1.06 kg surrounded by anti-Compton detectors with NaI(Tl) and CsI(Tl) crystal scintillators. Using 4712 and 1250 hours of Reactor ON and OFF data, respectively, limits of the neutrino magnetic moment of mu_nu < 1.3(1.0) X 10^{-10} mu_B at 90(68)% confidence level were derived. Indirect bounds of the nu_e_bar radiative lifetime of m_nu^3 * tau_nu > 2.8(4.8) X 10^{18} eV^3 s can be inferred.