Potential for large germanium detector arrays for solar-axion searches utilizing the axio-electric effect for detection

Abstract

The sensitivities of large arrays of low-background germanium detectors for solar-axion, or axionlike particle, searches are investigated in the context of several coupling scenarios. A search was made for the 14.4-keV axion branch from the M1 transition in the thermally excited $^{57}\mathrm{Fe}$ in the solar core in $80\text{ }\text{ }\mathrm{kg}\text{ }\mathrm{d}$ of data from the International Germanium Experiment (IGEX) Dark Matter experiment. In one scenario, the direct couplings of axions to hadrons and to electrons were assumed to be in the range of the Peccei-Quinn scale $3\ifmmode\times\else\texttimes\fi{}{10}^{5}\ensuremath{\le}{f}_{\mathrm{PQ}}\ensuremath{\le}7\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{ }\mathrm{GeV}$. This scenario is excluded by the IGEX data. In a second case, at the same Peccei-Quinn scale, coupling to photons and to electrons is suppressed. The IGEX data partially exclude this scenario depending on the degree of suppression. In the third case, the Peccei-Quinn scale for all couplings is assumed to be in the range $3\ifmmode\times\else\texttimes\fi{}{10}^{6}\ensuremath{\le}{f}_{\mathrm{PQ}}\ensuremath{\le}7\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\mathrm{GeV}$. Detection rates in Ge for all three scenarios are presented for several detector arrays.