Search of Neutrino Magnetic Moments with a High-Purity Germanium Detector at the Kuo-Sheng Nuclear Power Station

TL;DR

This study used a high-purity germanium detector near a nuclear reactor to set new limits on neutrino magnetic moments, achieving low detection thresholds and background levels to improve sensitivity.

Contribution

It presents the first experimental search for neutrino magnetic moments at a nuclear power plant using a high-purity germanium detector with advanced background suppression.

Findings

Set a new upper limit on neutrino magnetic moments of 7.4 x 10^{-11} μ_B at 90% CL.

Achieved a detection threshold of 5 keV and background level of 1 count per day near threshold.

Provided indirect bounds on neutrino radiative decay lifetimes.

Abstract

A search of neutrino magnetic moments was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 $\cpd$ near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron anti-neutrino flux of $\rm{6.4 \times 10^{12} cm^{-2} s^{-1}}$, the limit on the neutrino magnetic moments of $\rm{\munuebar < 7.4 \times 10^{-11} \mub}$ at 90% confidence level was derived. Indirect bounds on the $\nuebar$ radiative decay lifetimes were inferred.