Search for hadronic solar axions

Resonance excitation of the ⁸³Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism and via an M1-transition in the ⁸³Kr nucleus in the Sun is searched. The γ-and x-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a proportional counter in the underground low-background facility of Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion-photon coupling constant and the axion mass: |g _Aγ m _A| ≼ 6.16 × 10⁻¹⁷. In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of m_A ≼ 12.6 eV at 95% coincidence level (C.L.). In case of pure hadronic interaction the upper limit for axion-nucleon coupling is $|g_{AN}^3-g_{AN}^0|$ ≼ 8.3 × 10⁻⁷ at 95% C.L., which corresponds to upper limit for hadrionic axion mass: m_A ≼ 64 eV at 95% C.L. with the generally accepted values S = 0.5 and z = 0.56. (paper)