Measurement of neutrino-electron scattering cross section and the EW parameters at the Kuo-Sheng reactor neutrino laboratory

Abstract

The ν̄e−e− elastic scattering cross-section was measured at the Kuo-Sheng Nuclear Power Station with a CsI(Tl) scintillating crystal detector array with a total mass of 187 kg. The detector was exposed to a reactor ν̄e flux of 6.4 × 1012 cm−2s−1 originated from a core with 2.9 GW thermal power. A cross-section ratio of Rexpt = [1.08 ± 0.21 (stat) ± 0.16 (sys)] × RSM was measured. Constraints on the electroweak parameters (gv,gA) were placed, corresponding to a weak mixing angle measurement of sin2θw = 0.251 ± 0.031 (stat) ± 0.024 (sys). The destructive interference in the SM ν̄e-e processes was verified with the value of RINTexpt = [0.92 ± 0.30 (stat) ± 0.24 (sys)] × RINTSM. Bounds on neutrino anomalous electromagnetic properties were placed: neutrino magnetic moment at μν̄e < 2.2 × 10−10μB at 90% C. L., and the neutrino charge radius at <r2νe> = [0.61 ± 1.30 (stat) ± 1.01 (sys)] × 10−32 cm2.