Study of a Coherent Elastic Neutrino-Nucleus Scattering experiment at a reactor with a PbWO4-based bolometer

Abstract

The first observation of the Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) by the COHERNET experiment using accelerator neutrinos rendered opportunities for abundant scientific and technological applications. To study the CEνNS process precisely, a project using cryogenic bolometer technology with lead tungstate (PbWO4) as a detector candidate and a nuclear reactor as a neutrino source is proposed. By taking a typical reactor, the China Taishan Nuclear Power Plant, as a reference, a flux of 6.7×1016 m−2 s−1 with energy below 10 MeV can be realized at an experimental site located approximately ∼30 meters away from one of the 4.6 GWth thermal power Taishan reactor cores. The specific heat of PbWO4, which is an important detector research and design parameter, was measured for the first time at O(500) mK, and the results were found to be consistent with the prediction of Debye model. The phonon-only response of a PbWO4 crystal to the energy deposits at very low temperatures may offer high sensitivity to the small nucleus recoil CEνNS signal. A configuration using a one-gram PbWO4 cube as a detector unit working at a temperature of O(10) mK, together with novel phonon sensor technology sensitive to nucleus recoil energy as low as O(10) eV, is hypothesized as the ideal experiment benchmark. Consequently, a signal rate of around 200 reactor neutrino coherent scattering events can be expected per day with a one-kilogram PbWO4 detector volume, against ∼20 background counts in the optimized signal region.