Theνe − e − elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal array having a total mass of 187 kg. The detector was exposed to an average reactorνe flux of 6.4 × 10 12 cm −2 s −1 at the Kuo-Sheng Nuclear Power Station. The experimental design, conceptual merits, detector hardware, data analysis and background understanding of the experiment are presented. Using 29882/7369 kg-days of Reactor ON/OFF data, the Standard Model (SM) electroweak interaction was probed at the squared 4-momentum transfer range of Q 2 ∼ 3 × 10 −6 GeV 2 . The ratio of experimental to SM cross-sections of ξ = [1.08 ± 0.21(stat) ± 0.16(sys)] was measured. Constraints on the electroweak parameters (gV , gA) were placed, corresponding to a weak mixing angle measurement of sin 2 θW = 0.251 ± 0.031(stat ) ± 0.024(sys ). Destructive interference in the SMνe−e process was verified. Bounds on anomalous neutrino electromagnetic properties were placed: neutrino magnetic moment at µν e < 2.2 × 10 −10 µB and the neutrino charge radius at −2.1 × 10 −32 cm 2 < r 2 νe < 3.3 × 10 −32 cm 2 , both at 90% confidence level.

A search of neutrino magnetic moments 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 kg −1 keV −1 day −1 near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron anti-neutrino flux of 6.4 × 10 12 cm −2 s −1 , the limit on the neutrino magnetic moments of µν e < 7.4 × 10 −11 µB at 90% confidence level was derived. Indirect bounds on theνe radiative decay lifetimes were inferred.

A new detection channel on atomic ionization for possible neutrino electromagnetic interactions is identified and studied. Significant sensitivity enhancement is demonstrated when the energy transfer to the target is of the atomic-transition scale. The interaction cross section induced by neutrino magnetic moments () is evaluated with the equivalent photon method. A new limit of ð " e Þ < 1:3 Â 10 À11 B at 90% confidence level is derived by using current reactor neutrino data. Potential reaches for future experiments are explored. Experiments with sub-keV sensitivities can probe to 10 À13 B. Positive observations of in this range would imply that neutrinos are Majorana particles.

No abstract

Abstract. The article describes the research program towards an experiment to observe coherent scattering between neutrinos and the nucleus at the power reactor. The motivations of studying this process are surveyed. In particular, a threshold of 100-200 eV has been achieved with an ultra-low-energy germanium detector prototype. This detection capability at low energy can also be adapted for searches of Cold Dark Matter in the low-mass region as well as to enhance the sensitivities in the study of neutrino magnetic moments. Neutrino coherent scattering with the nucleus[1]is a fundamental neutrino interaction which has never been experimentally observed. The Standard Model cross section for this process is given by:where m N , N and Z are the mass, neutron number and atomic number of the nuclei, respectively, E ν is the incident neutrino energy and T N is the measure-able recoil energy of the nucleus. This formula is applicable for E ν < 50 MeV where the momentum transfer (Q 2 ) is small such that Q 2 R 2 < 1, where R is the nuclear size. Although the cross-section is relatively large due to the ∼N 2 enhancement by coherence, the small kinetic energy from nuclear recoils poses severe experimental challenges both to the detector sensitivity and to background control. Various detector techniques have been considered[2] to meet these challenges. Measurement of the coherent scattering cross-section would provide a sensitive test to the Standard Model [3], probing the weak nuclear charge and radiative corrections due to possible new physics above the weak scale. The coherent interaction plays important role in astrophysical processes where the neutrino-electron scatterings are suppressed due to Fermi gas degeneracy.