Measurement of Neutrino-Electron Scattering Cross-Section with a CsI(Tl) Scintillating Crystal Array at the Kuo-Sheng Nuclear Power Reactor

TL;DR

This study measured the neutrino-electron scattering cross-section using a CsI(Tl) detector at a nuclear reactor, testing the Standard Model and setting limits on neutrino electromagnetic properties.

Contribution

First measurement of neutrino-electron scattering cross-section with a CsI(Tl) scintillator at a nuclear reactor, providing new constraints on electroweak parameters and neutrino properties.

Findings

Measured cross-section ratio of 1.08 ± 0.21(stat) ± 0.16(sys)

Determined weak mixing angle s2tw = 0.251 ± 0.031(stat) ± 0.024(sys)

Placed bounds on neutrino magnetic moment and charge radius

Abstract

The $\bar{\nu}_{e}-e^{-}$ elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal array having a total mass of 187kg. The detector was exposed to an average reactor $\bar{\nu}_{e}$ flux of $\rm{6.4\times 10^{12} ~ cm^{-2}s^{-1}}$ 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 $\rm{Q^2 \sim 3 \times 10^{-6} ~ GeV^2}$. The ratio of experimental to SM cross-sections of $ \xi =[ 1.08 \pm 0.21(stat)\pm 0.16(sys)] $ was measured. Constraints on the electroweak parameters $(g_V , g_A)$ were placed, corresponding to a weak mixing angle measurement of $ \s2tw = 0.251 \pm 0.031({\it stat}) \pm 0.024({\it sys}) $. Destructive interference in the SM $\nuebar -$e process was verified. Bounds on anomalous neutrino electromagnetic properties were placed: neutrino magnetic moment at $\mu_{\nuebar}< 2.2 \times 10^{-10} \mu_{\rm B}$ and the neutrino charge radius at $-2.1 \times 10^{-32} ~{\rm cm^{2}} < \nuchrad < 3.3 \times 10^{-32} ~{\rm cm^{2}}$, both at 90% confidence level.