Searches for axions with the EDELWEISS experiment

Abstract

The EDELWEISS experiment primarily aims at the direct detection of WIMPs using germanium bolometers. It is also sensitive to the low-energy electron recoils that would be induced by axions. We present new constraints on the couplings of axions using data from the EDELWEISS-II experiment. Using a total exposure of up to 448~kg.d, we searched for axion-induced electron recoils down to 2.5~keV within four scenarios involving different hypotheses on the origin and couplings of axions. We set a 95~\% CL limit on the coupling to photons $g_{A\gamma}<2.15\times 10^{-9}$~GeV$^{-1}$ in a mass range not fully covered by axion helioscopes. We constrain the coupling to electrons, $g_{Ae} < 2.59\times 10^{-11}$, similar to the more indirect solar neutrino bound. Finally we place a limit on $g_{Ae}\times g_{AN}^{\rm eff}<4.82 \times 10^{-17}$, where $g_{AN}^{\rm eff}$ is the effective axion-nucleon coupling for $^{57}$Fe. Combining these results we fully exclude the mass range $0.91\,{\rm eV}<m_A<80$~keV for DFSZ axions and $5.73\,{\rm eV}<m_A<40$~keV for KSVZ axions.