Search for axions from the Kuo-Sheng nuclear power reactor with a high-purity germanium detector

Abstract

A search of axions produced in nuclear transitions was performed at the Kuo-Sheng Nuclear Power Station with a high-purity germanium detector of mass 1.06 kg at a distance of 28 m from the 2.9 GW reactor core. The expected experimental signatures were monoenergetic lines produced by their Primakoff or Compton conversions at the detector. Based on $459.0/96.3$ days of reactor ON/OFF data, no evidence of axion emissions were observed and constraints on the couplings ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$ and ${g}_{aee}$ versus axion mass ${m}_{a}$ within the framework of invisible axion models were placed. The KSVZ and DFSZ models can be excluded for ${10}^{4}\text{ }\text{ }\mathrm{eV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}{10}^{6}\text{ }\text{ }\mathrm{eV}$. Model-independent constraints on ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}\ifmmode\cdot\else\textperiodcentered\fi{}{g}_{aNN}^{1}<7.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}2}$ for ${m}_{a}\ensuremath{\lesssim}{10}^{5}\text{ }\text{ }\mathrm{eV}$ and ${g}_{aee}\ifmmode\cdot\else\textperiodcentered\fi{}{g}_{aNN}^{1}<1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ for ${m}_{a}\ensuremath{\lesssim}{10}^{6}\text{ }\text{ }\mathrm{eV}$ at 90% confidence level were derived. This experimental approach provides a unique probe for axion mass at the keV-MeV range not accessible to the other techniques.