New Limits on Coherent Neutrino Nucleus Elastic Scattering Cross Section at the Kuo-Sheng Reactor Neutrino Laboratory

Abstract: Neutrino nucleus elastic scattering ({\nu}Ael) with reactor neutrinos is an interaction under full quantum-mechanical coherence. It has not yet been experimentally observed. We present new results on the studies of {\nu}Ael cross section with an electro-cooled p-type point-contact germanium detector at the Kuo-Sheng Reactor Neutrino laboratory. A total of (242)357 kg-days of Reactor ON(OFF) data at a detector threshold of 200 eVee in electron equivalent unit are analyzed. The Lindhard model parametrized by a single variable k which characterizes the quenching function was used. Limits at 90% confidence level are derived on the ratio {\rho} relative to standard model (SM) cross section of {\rho}<4.7 at the predicted value of k=0.162, while k<0.285 at the SM-value of {\rho}=1. Prospects on future positive measurements are discussed.