Search of Axions from a Nuclear Power Reactor with a High-Purity Germanium Detector

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 mono-energetic 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 $\gagg$ and $\gaee$ 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 eV < m_a < 10^6 ~eV. Model-independent constraints on \gagg \gv1 < 7.7 X 10^{-9} GeV^{-2} for m_{a} < 10^5 eV and \gaee \gv1 < 1.3 X 10^{-10} for m_{a} < 10^6 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.