Final results of ν-bare — e scattering cross-section measurements and constraints on new physics

The ν-bare – e elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal detector array with a total mass of 187 kg at the Kuo-Sheng Nuclear Power Station. The detectors were exposed to a reactor ν-bare flux of 6.4 × 1012 cm−2s−1 originated from a core with 2.9 GW thermal power. Using 29882/7369 kg-days of Reactor ON/OFF data, the Standard Model (SM) of electroweak interaction was probed at the 4-momentum transfer range of Q2 ∼ 3 × 10−6 GeV2. 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). Destructive interference in the SM ν-bare-e processes was verified. Bounds on neutrino anomalous electromagnetic properties (neutrino magnetic moment and neutrino charge radius), as well as non-standard neutrino interactions were placed. We summarize the experimental details and results, and discuss projected sensitivities with realistic and feasible hardware upgrades.