The ${\overline{\nu }}_{\mathrm{e}}-{\mathrm{e}}^{-}$ 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 reactor ${\overline{\nu }}_{\mathrm{e}}$ flux of $6.4\times {10}^{12}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$ 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 $29882/7369\mathrm{kg}$-days of Reactor ON/OFF data, the standard model (SM) electroweak interaction was probed at the squared 4-momentum transfer range of $Q^2\sim 3\times {10}^{-6}{\mathrm{GeV}}^2$. The ratio of experimental to SM cross sections of $\xi =[1.08\pm 0.21(\mathrm{stat})\pm 0.16(\mathrm{sys})]$ was measured. Constraints on the electroweak parameters ($g_V,g_A$) were placed, corresponding to a weak mixing angle measurement of ${sin}^2{\theta }_{\mathrm{W}}=0.251\pm 0.031(\mathrm{stat})\pm 0.024(\mathrm{sys})$. Destructive interference in the SM ${\overline{\nu }}_{\mathrm{e}}-\mathrm{e}$ process was verified. Bounds on anomalous neutrino electromagnetic properties were placed: neutrino magnetic moment at ${\mu }_{{\overline{\nu }}_{\mathrm{e}}}<2.2\times {10}^{-10}{\mu }_{\mathrm{B}}$ and the neutrino charge radius at $-2.1\times {10}^{-32}{\mathrm{cm}}^2<⟨{\mathrm{r}}_{{\overline{\nu }}_{\mathrm{e}}}^2⟩<3.3\times {10}^{-32}{\mathrm{cm}}^2$, both at 90% confidence level.

• Received 9 November 2009

DOI:https://doi.org/10.1103/PhysRevD.81.072001